Cisco OSPF Training

1. Introduction to OSPF: Hi everyone and welcome to Cisco SPF training course. This course is all about dynamic routing protocol, OSPF. Ospf is the part of CCMP enterprises. Well, it means if you learn this training course, so it is a gateway for your CCMP as well. First few minutes, our theory about the topic. And then we're gonna do a demonstration and Eve and g simulation. This training core from basic to advance about OSPF. This training courses mix-up theory and demonstration. This course we can learn dynamic routing protocol, OSPF, how to configure dynamic routing protocol, OSPF, OSPF different tables such as diaper table topology table, routing, table, OSPF, metric calculation, OSPF packet type and OSPF packet header. Ospf part selection, optimisation, OSPF, different terminologies. Who SPF summarization, OSPF, router ID selection, different router type and different route type. Dr. DR. Election, who is pure filter access control list, basically interfaces, network type and load balancing. This course is designed for new IT professional with or without experience and network engineer looking to polish their dynamic routing protocols scales. The topic core in this course can help the student to prepare for CCNE and CCMP exam as well. Thank you very much to join this course. 2. Concept of OSPF: So now we are starting OSPF, open Shortest Path First protocol protocol. We know setup rules and regulation. And OSPF is also a dynamic routing protocol. Sam like EEG, ERP, OSPF, Open Shortest Path First, which we discussed previously as well, and the routing section, OSPF coming under link-state routing protocol. We done three different category. One was the link-state routing protocol and otherwise hybrid routing protocol. And the third was the report one, end report Gen2 distance vector routing protocol coming from the hybrid routing protocol we cover EEG ERP. Now from the link-state routing protocol to protocol are coming under this category, IS-IS. And another one is OSPF, which is a link-state routing protocol. Link-state when the link come up and goes down at center update. That's why we call them link-state. Link means the interface, that means the status and protocol means set up rules and regulation. So everything related to the link of the interface, maybe the bandwidth, maybe link is up or down. The cost of the link, the bandwidth of the link, the delay of the learning. All these things are called link state, either link status. So that's why this protocol is called link-state routing protocol. Ospf is also dynamic routing protocol. We then two categories, static routing protocol and dynamic. Dynamic means, which get each and everything dynamically. They'll learn that out dynamically. They changed the part dynamically when something's changed. So they will learn automatically, not like a static routing protocol. And it is an open standard. Open standard means you can enable OSPF on any vendor. Maybe the router, maybe what is called Juniper router, maybe Cisco router, any vendor. So you can enable OSPF routing protocol. That's why we call them open standard. This is link-state dynamic routing protocol. Ospf is using Shortest Path First SPF algorithm. Basically the algorithm name is, or maybe I mentioned here this. Okay, I did not mention that one. But anyway, they are using SPF algorithm. Wispy of external and internal administrative distance is wanting. It means in the ranking it is on 1110. Year GRP was 90, but externally it was 170. So this is the difference. Ospf internally or externally. If you redistribute, either use internally, the LED value is one to n, and we know administrative distance. Ospf is classless routing protocol and the metric is cost. Metric we know. So cost is means the bandwidth. Basically, we will do the molar, how they are finding out the metric of the OSPF similar like a year GDP. We will do the metric up with PFAS will always be of use multicast address 24224005 to send the halo packet. Like AGRP. It was using 224009 something to send the Hello packet. Ospf also use two to 4006 for a DRP. Dr. we will do the RBD are so forget about this one. Then they're using different multicast IP. The halo timer is 10 s and you're dead time or is 40 s, it means the halo and deadtime are exchanged. Then EEG ERP. Okay, now let's peer support, VLSI M and route summarization. Now we get somehow concept of summarization because we've done an ERP, we minimize the routing table. So the same thing can be applied. And OSPF Israel, who is pure file to use wildcard mask. Wildcard is basically the opposite of subnet mask when you configure SPF. So you need to put a wildcard and we put a wildcard in here, GRPs will always be of support MD5 and clear texts authentication. Their support both authentication method, which is in the next outline, not in this course. We will do the, you can protect the protocol so nobody can join you without the key. And that key can be through md5, either clear text. Whereas peer support summarization only an ABR. We will do a B or what is the APR? So forget about this one. Who is P of our require more memory and CPU, no doubt. Because OSPF is the only protocol you can configure on huge unlimited routers. Eirp can be supported by different 100 and you can tune them out to two to 55. Rep can be configured up to 15. But OSPF is the only protocol which can you configure an unlimited router. So that's why they require more memory and CPU to process P of work on based on area. And areas. As Carl big bone, because it's a huge protocol there, divide them and area. An area is like a big bone in our body. We have a backbone. So which join all our body. And without your backbone, your body is good for nothing. You will delay in the table, I'm sorry, in the bed. Similarly, OSPF has area zero, which is a big bone area. We will discuss area and type of area later on. Spf is also three different types. Terrible, seemed like an ERP, neighbor table, topology table, and routing table. Again, we're going to discuss these three tables separately. But anyway, SDR and the introduction wispy of packet are only sent to the neighbor and their own area. Because it's a huge protocol like a branch manager. And we will suppose one company has many branches like a Microsoft or Cisco. So every area has their own manager to maintain each and everything up dead areas only. So similarly, OSPF packet are only sent to the neighbor within the area. They can pass to the other area, but their job is of some other router. Ospf support both IPV4 and IPV6, no doubt same like AGRP. Do load balancing but only equal load balancing, not unequal to lose. Their teacher is only an EEG ERP. Ospf can do load balancing Israel equal. And now we know what is load balancing, at least you get the idea then what is equal and unequal load balancing? And OSPF is a dynamic protocol. We support unlimited hop count. I already told you about this one. And what they do when they send the update. They will start from this number. I will shoot you in the table. They will increase this number whenever there is a changes, so they will increase. And the last digit is this one. When they reach to this one, then the counter will set to this value back again at 00001. This is the way to update the number. By this number, they will increase every time. If there is any updates. They will increment them by one every update. And when they reach to this value, that will make them again this value and start again. This is the way how their sequence number working with peer protocol is more complex to set up and hard to troubleshoot. No doubt, these protocol anomaly configure and our ISPs backbone as well, IS-IS. And this protocol, normally you will see most of the time and most widely used protocols, OSPF and every organization. This is more complex, no doubt because there are many thing. This is called link-state routing protocol, OSPF. Ospf, each router maintain a complete map of the network topology. So OSPF is a protocol. They know the entire map of the network. How is like a Google Map? We knew on the Google map. So you know, all the parts still from your source to destination. And how many gas station out there, how many things are there? They will show you each and everything in the map. So similarly, OSPF, they maintain the complete map of the network topology. Know what is where. And if anything goes wrong, something goes down. Okay? So accordingly to the map, they will calculate the shortest path to reach to the destination. And this is the algorithm I forgot this one, the algorithm ditch Castro algorithm, something. I don't know how to pronounce them. The customer algorithm they're using this algorithm, ERP was using dual algorithm. They're using this algorithm to find out the best path. And the result part then stored in the form of routing table. So the best route will be installed in the routing table. This is the way how OSPF is working and how they maintain the entire map of the topology is like a Google map. They know everything. So every router know in OSPF configure router know each and everything up the entire topology. You get the idea. And when we configure OSPF, so listen the neighbor and collect all the link-state information. And link-state information can be the cost of the interface, the bandwidth of the interface, the part of the interface and professors up the interface is down and all those things and they will collect those information and they will install them and the topology database, which we call them link-state database. Anyway, we will discuss these terminology later on. And then they will calculate the shortest path to reach to the destination. This how OSPF is working. Another way, SPF is widely used routing protocol and especially in large enterprise network and use based on the routing protocol. And you can find out these protocol is a big bone I allergy to you like an ISP service provider, network and major routing vendor, Cisco Juniper, all of them support OSPF. And mostly you will see a new or ISP network and the enterprise network. Every beer is who SPF, nobody is using AGRP because they have many complications of those two protocol. So mostly you will find who SPM. And finally, basically always pay Visa hierarchical routing protocol. They held the complete map up the routing table. Then because there's a huge protocol. So they are subdivided into the routing area and the main area we call them the areas zero, which is a 32-bit number. Because you can type the area zero either you can die by 0000 is basically like this. But normally we type them in zero. I will tell you in the lab when we do, if I remember, I will show you a 32-bit number, the area number by typing and four digits, either like IP address and either you can type directly. So we have to wear to express this in decimal number either in Dart decimal notation. Same IP for this area. Okay? So this was OSPF introduction that what is OSPF and how it is work. And some important point which I highlight, okay. 3. OSPF Terminologies: Next we're going to discuss some terminology related to OSPF. The first terminologies area and OSPF because it's a dynamic routing protocol and support unlimited hop count. Okay? So they are divided and area is like a subnetting. So we call them area, like as I give an example, if you have a huge network, either if you have a huge companies and every We're like a Microsoft, Cisco and aldose. And you have many branches all over the world. So what you will do in every branch, you have a separate area manager and they will maintain that area branch, not one manager to maintain Aldi offices, which is difficult. So similarly, because you SPF is a huge protocols, so they divide them. An area, area is Nika subnetting division. So it allows separation of large enter network into smaller networks. And we call them area to divide them and smile area. And the main branch, we call them a big ball. That area is called big boned area and other areas called off big bone. So big bone and area of big bone. So area is called backbone. Other area is called area of big backbone. So the main branch and we have branches, head office, and we have our branches because we have a huge network all over the world. So we divide them and every branch has a separate manager. So similarly, OSPF is a huge protocol. They're divided them in area, and area is basically a small network and they will exchange routing table. In this way, the routing table will be minimized and the maintenance will be AC and less CPU and RAM will be required to maintain a smile routing table if you keep them as a one. So it will become an issue. So that's why it's called area backbone. So Open Shortest Path First is a big ball. Center point is like a head office. And all the area has to be connected to the backbone directly. Either indirectly. Let me repeat. All the area has to be connected to the backbone, which is areas zero. It has to be connected directly, either indirectly or directly. Every area has to be connected, otherwise, it will not be the part of OSPF. There is a way to link we call them, which we will discuss in the second paper. If you are areas away from areas zero, there is no way to connect two areas zero. So what you can do, then you can end directly connect that area. We call them virtual link and OSPF. The main area is called backbone area and Beckman area is nothing but area is zero, which maintain all the complete database of the entire network and they know each and everything like a head office. So I'll branches has to be connected to the head office. And they will share out the detail to the head office in the end of the day. There, these are our activity and let me share you because you are our head office. Here. The head office is called backbone, which is an area zero. I hope that's clear. Then area of big bone. Any either any other areas besides areas euro is called area of bed born. And they maintain a separate specific database and stood up Complete database. Every branch, suppose you have a company, Microsoft and they have a branch in India, they have a branch in UK, they have a branch in USA, they have a branch in Pakistan. So everywhere you have a branch manager, they will maintain only dead branch only. And they don't know the head office? Yes. Head office will know each and every branch detail. But the branch is not required to maintain the head office detail. They will just share their own detail. So definitely any other area beside areas uterine scar, area of big bone such as the area one, area two, area three, area four, area five. And they all has to exchange the information to zero and there has to maintain their own detail, not the entire detail. The things our speed of the convergence time is quicker. Okay, So this area of backbone, now coming to another terminology related to OSPF, router ID. Every router when you configure an ear GRP, either in BGP, either an OSPF. We'll choose one IP, which is not an IB, but it is same like IP, which we call them router ID, which is unique to identify the router and the entire network. It's like a name and the house. Every brother has a different name, unique name. You cannot give the same name to your three brothers, which is not possible. The communication will not be possible in the school and college. Answered the house. Everybody, you can not give them same name to three brothers. Similarly, Router ideas a unique number to a same Liga, IP address, but it's not IP address. It is same like IP address. I will do, I will, by the way, I will show you this one when we do the lab. So I will assign another number, same like IP and then they will take them. But anyway and normal way, they will take the IP address and we'll make them as a router ID and how they are taking. So we will discuss this in the router ID selection process. First, they take the highest IP address of logical interface, like a LoopBack. Loopback is not available. Then they will take the Saudi. The first one is they will take the men. Well, if you configure a manual router ID, they will take that one. If you haven't configured men will router ID. They will take the highest loopback interface and make them as a router ID. If Lubeck is not available, it will take the highest IP address of any interface. This is the way to select the router ID and the decking uniquely identify them. Anyway, we will see in the lab and we have a separate layer for Router ideas. Well, another is link. Link is basically guard the interface which is running OSPF. We call them link. When you enable OSPF process under the interface, either ND, what is called configuration mode. So we call them link. State means the status. The information associated with the interface is called a state. Like IP address of the interface interfaces up or down. The interface subnet mask, the interface IP address, the interface bandwidth. They interface delay the interface network type, the interface subnet mask. All those things are called the state of the interface. Another terminology is LSA, link-state advertisement as a data packet which contain link-state and link-state we discussed above. Link means the interface state means the information. So when the Beckett keep the information up the link, like the cost of the link bandwidth up the link IP address of the link, subnet mask of the link, I'll lose information. Who is carrying these information is called link-state advertisement. So link-state advertisement at our data packet with Katie, the link-state information, and they send them to the other router. We call them LSA, link-state advertisement, advertisement when to advertise something. So they will carry out the link information and we'll give it to the other routers. So we call them LSA. Then L S dB, SDP means link-state database. We just discussed LSA. And when the other router get these LSA. So they will make our database of these, which we call them SDP, means link-state database. The link information which I will get, I will put them in the table and their table, I will call them link-state database. They call them link state database. How they're getting. We will do this in detail anyway, as mentioned here, how they are getting these link information. Another terminology related to OSPF is internal router. It is a router that has only OSPF neighbor relationship with the same area. So like this one. So this is always p of zero and this is where SP of areas zero. So this router is Carl Internet router. Either this router or five belonged to OSPF area to our food is called OSPF area one. All the interfaces fall in one area, so we call them Internet routers and Backbone router, the router which is configured in areas zero. So in this case, R1 is big bone here I mentioned as well. So R1 belonged to areas zero. So that's why it's called a backbone router. Then we have our designated route and backup designated row. Again, we will do a small level related to DR. DR. And shortcut. We call them DR. Video. If you have a broadcast segment. So what they will do, they will make one router is a king. Why? Because if you have a router in broadcast domain, and I do that, every router has to send Hello packet after every 10 s. So they start to send a halo packet. What will happen? They will start hello, hello, hello, hello, because they are in the same broadcast. So R1 Wilson to R2, R2, R3, R4, R5, R6, R7. And it will make like a broadcast domain. And it will be like strong. You see, it's like a DRP DREs concept like when we were working in the previous company. So we were six guys working the same job. From India to from Pakistan and two from Sudan. What they say. So every time when we have an issue to individually everybody go to the manager that I have this issue and I need training, I need certification. I knew disinformation. I need I need HLB. Now when I go after awhile, another guy go to him, that I need vacation, another one go then I need to go to NDI, need to day off another. What the **** is this? Everybody is coming to me. Let's do another thing. I will make one guy, DR. DR. Means the person who represent all of you, all of your six guys. Whenever you have an issue, you need to share with him and he has to come to me. Not all of you. We were six guy and look at he become angry. But if you are more than this, it means everybody will go to him individually. So what you need to do, so OSPF do the same thing if they have a same broadcast domain and router are connected with each other. So they say, okay, because we need to send a halo packet to each other every time and whenever there is an update, we need to send up there to each other. And it will make an issue if there is network down, everybody has to send a query request and everybody has to reply. So it will make an issue for us. Why not make one router is a DR. Now there is a process who are gonna be there, DR. So rather than to send the packet to each other, they will send the packet to DR. Now in case DR is not available, the person which is like our what is called team leader if he is not available. So we have backup designated router. It means there will be alternative one here, gonna become the team leader and he will manage everything. So similarly, they say, Okay, one will become DR., another will become B DR. if DRS down beauty or is the responsibility you need to send the request to them has then he will become the DR. Now, how the DRM beauty or select the eyes are different topic. But here we just need to discuss what is DR and video and why we did this one. To stop the broadcast strong. And to start the, it will send the entire topology to each other again and again. If you are not selecting the RBD are how they are selecting, we will see in the upcoming classes, but anyway, these are the RBD. Now there is another concept, our router priority. And this is the thing which play a role to select a DR and BTL. Superiority means maybe one guy, their health, some what is called characteristics up the team leader. Not everybody can not be a team leader properly. Somebody had maybe they have a good experience, may hear there. Good degree, or maybe they have some other knowledge, or maybe they held and some management tasks. So you can make dead guy as a team leader. So similarly, to select a DBDR, they need a router priority. So by default the spirit is one. And our router, this priority is one. And display the role to make and become DR and BTL. The value ranges 0-2550 means date if you set the priority zero, so they say, Okay, I don't need any team leader. I don't want any team leader. I will go directly to the manager. It means they will not participate in the election. And 1-255, you can put them anywhere you this way, the highest value, it will become the DR. So suppose in this case, this router idea is 111, priority is 100, and here the product is 50. So this will become full and DR, and because nobody else is there, so this become BGR this way because the router priority is high here. So you can increase by default is one. So then they will, the tiebreaker will be the router ID. The one with the highest router ID will become the DR. So because here we changed the priority hundreds. So that's why this become the, if it is one and this is one, then this R2 will become the DR, because of priority is similar. So then the tiebreaker is router idea and router ID will never be the same. So this is the tiebreaker. So this is called Router priority. Then we have another 23 concepts related to OSPF, area border router. We call them a BRI duty. And last slide that I will tell you, what is ABR? Area border router area border routers that connect to one or more SPF area. A skull area border router, normally a router which connect other area. Too big bone area is area border router. Let me tell you here. R2 is ABR and R3 is ABR. Because here is area one, here is area zero. They connect both area. So area is called APR. Similarly here we have area to, here is areas. So R3 is called ABR, is like a border border between German and the other country, Europe and England. So area border routers which connect more than one area to each other. They're drought risk area border router. And then we have our two normals, system boundary router. The router which connect you to the other routing protocol to the other countries. I would say there are two enormous system router. So let me explain you from this topology. Here we have area one and here we have areas, areas us, big bone area. And all the router which is in this area is called internal router. Because all the router running, all the interfaces of these routers are in the same area. So we call them and tell the router similarly are six and 8.4. They belong to the same area. All the interfaces are in the same area configured, so we call them and turn the router. So there are also internal, there are also internal, however, are is not internal. The reason is our FY21 interfaces connected to outside BGP because he can into another protocol. So this our Firebase, a SPR, router. Three interfaces are connected to area V1, but however, one interface is connected to outside protocol. So this R5 become a SPR because these are five connect us to another routing protocol, OSPF. But R3, one side is connected to area 1.1 side is connected to a zero. So R3 is called ABR. This is ASB or this is a beer because our three connect to area, area and area 11 hand is an area one, another hand is an area zero. So they couldn't vote area. We call them the area border router and Backbone router. Router, which one or other interfaces belong to. Zero is called backbone router. Backbone because backbone area, area is zero. So any router, which one interface are more than one interface belonged to areas euro scalp backbone router, R1, R2 are nine, R7 and R3 are backbone router is when our three player to roll. It is a big bone router because one interface belonged to areas euro and also a desert ABR is connect to area. So this router play a role. Here. This is a SPR because our five connect with PF2 external routing protocol. This is called backbone area because all the routers belong to areas zero and this is non backbone area because this is not a zero. So any area beside areas is called non big bone area, either off big bone area, which we discussed, the tip. So this is wondered router and these are the some terminology. I hope so you understand this is HBR, this is ABR to connect to different area. That's it. 4. Configure OSPF: Last time we discussed theoretically OSPF and also some terminology related to OSPF. Now we're gonna do the lab related to OSPF. So this is our topology. This is the same topology which we use for EEG ERP as well. We have five routers, R1, R2, R3, four, and 5.2 VPC, VPCs, witchy the systems. Okay? So this is the same topology you already know, but this time I divide that topology. So this yellow, this is OSPF area zero, which we call them backbone. This is OSPF area one, this side, and this side we have OSPF area R2 and R4. We held some Lubeck interfaces, and here we have also some Lubeck interfaces similarly, which we use in EEG ERP, and the router image we use. And this topology is the same, which we use an ear GRP client, PCS, VPC. And for testing OSPF, we're gonna do our labor related to OSPF and the same topology and OSPF process ID we're going to use one. You can change, doesn't matter. Let me go to the topology here. I added this more Lubeck interfaces. We're going to use this later on. And I put here some other stuff like a backbone ABR. This side is also ABR, internal router, internal router. And this one is a SBIR. We're going to discuss these terminology later on. So I just put on the top of the router so it will be easy to distinguish them. And everything is same from R2 to R1. We have ten dot one dot 12. From R1, R2, R3 we held ten dot one dot 13. And from R2, R3 we held ten dot 123. So what are we held ten dot one network 12. So it means r1 to r2 and this side 13, so R12 three and this side, R2 to R3. So we held 23 and R2, R4. So we tend to 24 and R3 to R5. So we tend to get 135. And loopback interface is definitely So we're gonna taste more thing. And this side we have 190-21-6081. And they said we have 192 to 168 to one dot one is this router IP, and ten is the PC1 IP. Similarly, this side is two dot one or phi by p and 210 SPC to IP. So our main purposes, they're PC1 can reach to PC2 and vice versa, PC to reach to R1, sorry, PC1 with the help of OSPF. Similarly like an EEG ERP. And we're going to see more stuff as well related to OSPF. So first thing first, I need to copy paste the IP. Okay? Here we have a loop. Biggest one is, well, okay, so let's go to the same. This is the same thing. I will go to change the host name and IP domain lookup and exit die mode synchronization and create one Lubeck. This one. Then go to G zero, slope zero, this one to assign 12 to IP. And this side are tender 13 IP, okay? So it's easier, simpler like ERP. So let me copy this one. I already opened all these routers. So let me go to R1 and enter. Okay, and just paste. Nothing is configured inside this router. Even the name is different. So let me paste this one, and now it's done. Let's go to R2. So let me click on A2 to bring them on. And now this is R2. R2 has three interfaces, or ten dot one, dot 212, da2, 23 dot one, and this side 24 dot one. So this 12224 dot 123 dot one. And the other is basic stuff. You already know this one. So let me copy this one and let's go to R2 and just paste. Okay, and here it is. So R2 is already configured. Let's go to our three now. Okay, let me clear the screen and R2. So we have three interfaces to configure the IP addresses. 13, da2, 23 dot two, and this are 35 dot one. So three interfaces need to be configured. So let's go to this 11335 dot 1.23 dot two and some basic stuff. So let me copy this one, right-click copy, and let's go to R3 and paste. Okay, So let them apply so that we can verify or three years then let's go to R4. R4 we need to create many loop back interfaces. So what I need to do, let me show you our food has this one has two physical interfaces, are 24 dot 2.1 dot one this side, and 0-8, some loop back interfaces. So loopback interface zero to eight, and then two physical interfaces, IP. So let me copy this one. Copy and let's go to R4 and paste here. We change the host name and we create Lubeck for test purpose. Rather than to connect many system is better to create Lubeck. So it will represent a network and let's go to R5. R5 has similar, but however, the subnet is different. So let's go to R5. And let me quickly show you this is R5, two interfaces, 35-day CO2 and 21, and also some Lubeck interfaces. But this side is 172216 and this side is one cell to 230. So different subnet. Okay, so let's go to our file, copy this one, and right-click copy, and go to R5 and paste. Okay, let's apply this one. And finally we have two system to configure. So let's see, it's applied here. And now let's go to PC1 with BCAAs. So it's better to change the name Israel and also to assign one dot ten IP gateway one dot one. Because this is the gateway is important. You need to assign the gateway said PC name. This the command to set the name and paste and done. So it's chicken. And now let's save the city because we need to save all these setting to continue our lib type-safe. So it will save. Let's go to PC2. So PC2, we need to change the name, PC name. I said PC name, and copy this one. And let's go to PC2 and paste. So I say change the name. So it's changed the name and also the IPS two dot n and gateways to that one. And copy, sorry, type here saved, so it will save the city. Similarly, we need to sell this setting as well. So we're going to continue this left for entered OSPF configuration. So do right, here, do right as well, and here do right. And five do right to save the sitting and PC1, PC2, I already saved the setting to type this command. Save R1 is done. R2, R3, R4, and R5. Yes, So all of them is done. And now rest of the thing I will show you how to configure OSPF. So let's start from R1. R1 has three interfaces to advertise. The loopback interface for 44.10 dot one dot, and this are ten dot one dot 13. So I need to advertise all of these three and OSPF areas zero. We discuss areas zero, which is the backbone area. So let's go to R1 and configure R1 first. So let me maximize now and clear the screen. I'm in the configuration mode. First thing I need to type router, ISPF, and then the process ID, sorry, oh, SPF, and then the process ID. So we decide to put one. You can decide it shouldn't be same. You can put any in any other routers. But anyway, just for the simplicity, we will type one. And after that, I need to type router ID, router ID we're going to discuss. So I choose the router ID one dot one, dot one, if you haven't typed. So they will take automatically the loopback interface is id. We discuss theoretically that what is router ID, but later on in the course, maybe today or tomorrow, we're gonna cover how they choose this router ID and what is router ID. So I type Router ID1 11. It's like IP address, okay. But it's not IEP by the way. I told you last time as well now the network command To advertise. So the easy way is do show IP interface brief. I held three interfaces to advertise, basically on dynamic protocol. What is the procedure you need to advertise your own network. Similarly, other router will advertise their own network, and this way they will merge with each other. So I have three interfaces. So I will type the command network. And the first one is this one. So let me copy this one. But I want to advertise as a whole, so I will put zero. And after that in OSPF, you need to type wildcard. Wildcard is the opposite of subnet mask. So the subnet mask should be like this one. Yeah. Then the 30 to 40 to 52. So I need to make them opposite. Opposite will be 000 and the last will become a three. This is the wildcard last time, and I'll also show you where I want to advertise. Next thing you need to decide area. So type the area I told you last time and OSPF terminology there, you can type the area in two different way. And decimal formation and also in the IP address permit, okay? So you have two choices. Either just type zero, okay? It will take them. Let's do the other one with different way. So let me copy this one and let me paste because I need to just change the routine. Okay, My other interface is 13. So why not just 13, this one. And this time I will make area 0000. It's the same way. So it's up to you. You want to type the area in decimal value, either an IP address format and four dots. Okay? And the third one is I need to type the command network and then I need to advertise for that, for that one. Okay, So this is the last loopback interface because it's only single. So I will type 0000, okay, for time, they only check only the single IP and which areas we already know now area I can type zero. So zero means check this digits. Last term I'm ready to do. Zero means the first digit has to be for second 0434 and the last has to be one. But in this one, I said no, the last can be at last two digit, so it can be anything. What else do they said this was the way to configure OSPF. You just need to type the network which you want to give to your neighbor. Suppose if you don't want to, oh, share this network, just type no network. But however I want to share all the network, this one, this one, and this one. So I need to go to R2 now. So R2 has this one. R2 has three interfaces to advertise. Okay, so let's go to our two as well and type the command router or SPF one, and also network command. Better to type do show IP interface brief here and type your command, sorry, network command to advertise network. And this is the same network which was in R1 as well. So I can copy this one because they both have same this one. So I can paste this one here. So this trail in areas zero. Okay? So I need to type this ten dot, dot, this similar, and let me paste. And I held 24.23. Now, 23 is also in OSPF area zero. So let's go and make them 23. This one. I changed then that one-two-three and areas zero. However, the third one network, which is 1024, which not belong to a zero, I need to advertise that one, area one. So there is a small changes. I will make this area one. And here I will change 23 to 24 because I have three. So I advertise these two, sorry, this one and this one area is zero. And this one belong to area of one. So I put this in area one if you want to see. So it's better to show running and section SPF, SPF. So it will show you the entire OSPF configuration, which I've done here is I said router OSPF one. I want to advertise 12.23 and area 0.24 and area one. Okay, and now let's move to router three. So router three has this one. A router three has similar like R2. They have two interfaces in areas. 0.1 interface belong to area to area one. So this side is area to what I need to do. I need to go to R3 and do the same thing. So let me clear router or SPF one. And here, better type do show IP interface brief. And here what I need to do here, so this 23 has same. 23 is being advertised. R2 is, well, why not copy from there? 23. 23, because there's both have the same network. So let me copy this one and go to it will make it easier for us. So 23 is done. Now coming to 13. 13 is this one. So it's also belong to areas zero. So let me copy the same commands or not copy. Let me do it because I paste that one. So let me paste this one and just change this 113. Okay, this one, the first one, I advertise 13 now and 23 now, both in areas. However, the 3051, which is this one, you don't want it has to be an area. Area to what I can do. I need to copy this command to save some time and I need to paste. And the only thing I need to change is the third digits two through five. So let's go to chain the third digits, 235. And also I need to change the area to, to Done. And let's verify what I can do. Do show run and section or SPF and see did I advertised everything correctly or not? Okay. So here it is. What I started in areas 023.8 years, 0.35 AD or two with wildcard. R3 is done. Now I need to move to R4. R4 has many things are for all the thing is our area one. Okay? All these Lubeck interfaces, then D24, N1, nitrogen 168 dot one. So all the thing related to area one only. So let me clear the screen and type your router or SPF one and do a show IP interface brief. So many interfaces are there because we have Lubeck interfaces as well, zero to eight and we held two physical interfaces. So let me type network command, but by the way, is 24 is look like we have same network here as well. So I can copy from R to the network which I advertised and dot 24 both have the same one. So let's go to R2 and let me copy this one. It will save some time, and let's go to R4 because R4 and R2 here, same network. Yeah. So let me paste this one. I said I wanted what I extended warranty for wildcard, this area one. This one belonged to area one. Okay, so for this network is done. Now, next I had 19268 dot one network. So what I can do, let me go up and let me type one network, 1.2 to 16081 dot zero. Then the wildcard will be zero.00 and the last digit is 255. And area one, let me double-check. I held onto for subnet here. Here my subnet is 30. That's why I put three here also, I put the subnet mask, a wildcard three, because we held 30 subnet here is 30 subnet here is 30 subnet here is 30. But however, here I put 24 between these two devices. So that's why I put here 255 instead of three wildcard. You can quickly find out and Google as well, the subnet mask, and it will give you the wildcard. And also I have a calculator as well. I will share today there is another calculator as well. So they can find out these things for you. And if you know the concept, then you need to go back to the CCNV level stuff so that you will get the idea. Okay, So these three is done, sorry, these 21 network and tender, this one. Now I need to advertise all of these either one-by-one. Either I can do it to make them simple. So what I can do, let me type network 172, either copy up to this point, this one. Okay? And then the last also zero. And then I would say there the first is check, check the first ones they wanted to check and the check the second one. And third can be anything. And the fourth one can be anything. Because here the third digits are changing. 012-34-5678. And here it can be any value because these are the network 1-2 before. So that's why I say check the first 10 means check zero, second digits check 16. And the third digits can be anything. In the four digits can be anything. I can advertise this in area one. So let me show you, you will get the idea. Sure, running section or SPF. Okay, now let's see what we advertised. So basically I advertise all my Lubeck interfaces. I make them aloud in this subnet. And that's the one where they are connected to R2. And this one is the PC1 connectivity, this one, okay, we are done with this one. Now let's go to the other one. So what I can do, I need to copy this one. And let's go to Notepad. This the way you can do it. And R5, R5 has almost similar configuration. Here is what I can do. Let's check out. This should be 30. Yeah. Here is 10 to 230. So I changed it to 30 and area will be 2222. And the this network would be 35, instead of make them 35. This should be two. You get the idea why I'm doing it deliberately. I'm doing there so that you can get the idea. It doesn't mean that all the time you need to type yourself so that you can use to read all these things. So I copy from there and I change filtering because few things you need to chain. This was two. So I change this to two and the rest of the thing that same area to one cell to two, what was 16 year and here is 30 and area two. And finally we held 1035 and there it was 1024. Okay, so let me copy this one and let's go to our file and paste. So R5 pairs and PC1, PC2 is all the detail. You need to wait for awhile so they can reach each other and they can converge with one another. It's now doing, so, it's almost done up to that one. What we can do, let me save the settings, do, right? Because we're going to continue this lab with the same sitting, right sitting here, do right here is, right here is do copy running to startup. It's the same thing, okay, either right or this one. And here we already saved the sitting OK Control Z to clear the screen and Control Z to clear the screen and controls it to come out here and here. And our Firebase. So I hope so All of them has converge. Let's try to ping from PC1 to PC2, show ip, my IPS one dot then the opposite party IPAs are two dot ten. So let me just change the last digits in C. And I can reach to the other side through OSPF. So it means everything is working and I can try from this side as well. So show ip, my IPS two dot ten, I want to ping one dot ten from this side is also reachable. It means we've done the OSPF configuration correctly. So this was the basic configuration here. Let's move down. When we configure OSPF here as the R10 SPF configuration or the thing in area zero here. And I'll do some route or in areas zeros, sum of them is area one. And R3 we have some route and OSPF, areas zero and some of them and area two. And finally an R4. We have all the thing in area one. Here in R5, we have all the thing in area two. These are the command which we will use and the next slide when we check the tables. So definitely these command we're going to use the ear. And then we finally ping from PC1 to PC2. So everything is working and there are some few more command if you want to test. But anyway, we're going to test those in the other slide and if you want, so let's check out a show IP route to see the routing table and R1. So you can see R1 is receiving all the route all the way. And these are the route, these are some connected drought and local route. These are wispy or fraud, which we will discuss a bit later. Here you can see SPF route, okay? Also show q is p of database. If you want to check their topology table, we're going to discuss a bit later. And if you want to see show IP OSPF neighbor table. So we're going to discuss a bit later is also, here are the details and the main purposes we configure. And now the reachability is the, this is the way how we can configure SPF. And we have such topology which we use for EEG ERP as well. Next slide we're going to see different things related to OSPF one-by-one, like a year GRP. Next thing we're going to see the OSPF, different tables, like an EEG ERP. 5. OSPF Three Tables: Okay, so we configure SPF in our topology. Now let's verify three different table. Same concept like EEG ERP here in OSPF, we have also three terrible neighbor table, topology table and routing table. I hope so. We already know these three table from AGRP, neighbor table. They keep all the neighbor detail. The next hop router detail and interfaces detail. Okay, they are connected Nippur and OSPF topology table. Keep all the routes, whatever they'll learn, whatever all the information they keep and the topology table, this table, we also call them link-state database. Either FDB table as well, which is the topology table. Either we call them database table as well and shortcut. So topology table, database table, it is DB table, link-state database table. Basically whatever they learn, the entire topology, like the R1, R1 belonged to areas zero, but they know about area one and area two is well, similarly, this router belong to area one, but they know about OSPF, area zero and area two. This is called topology table because it's like a Google Map. I told you when you are on the Google Maps. So they will show you all the way, whatever coming in the way. They will show you the gas station. They will show the entire topology part. What is the data is or traffic or not. So all the thing. So similarly with SPF, keep that in the topology table. We call them topology table, either database table. And finally, we have our routing table. We're the best route to go to that topology table. From the topology table to routing table, okay, they copy the best route. So the first one is the routing table. Routing table. They will keep the best route in the routing table. And we'll use that part to forward the packet. Because the best part, the best route will go to the routing table if there are two things similar. So they will do the load balancing. We're going to discuss the load balancing as well, similar like EEG ERP. And they will keep the best route in the routing table and how we can verify the routing table. So the command is show IP route OSPF. Let's go to any router. And let's type here, show IP route SPF. I told them just soon issue merely stuff related to OSPF. Here is and if you go So there is all faraway SPF, SPF enter area and there is OSPF not supposed to be external. Type 1.2 as well. And there is type to Israel, E2 and E1 as well. So many things that are obliterated, which we will discuss later in the course. Not only 0, but there can be i as well. And so many other things. Similarly, they say, I learned many thing. This is the normal USB or fraud. They still destination ten dot 123. They still Destination, destination subnet mask 110. We already know this is the AD value administrative distance up OSPF ranking, which I told you in the ranking with PFAS and 110.2 is the cost. This already metric. Gases default molar, okay, So this is the metric like ERP. We find out the metric. So now today we're going to find out this to why they are showing me to hear and why they are showing three here. So we're going to find out about this one. This is the metric of this OSPF protocol. And this is the next hop where they will send the traffic if they want to reach to 1023. Okay? What else? This is the time they learn them, okay? And this the interface where they will exert to reach to this ten dot 123 destination. So let me go to R2 to do the same thing so that I can show you one example. So let me copy this command. And let me give an example of 1013. So 1013 is this 110113 are to say, I can go through this way to reach to tender 13. I have another way to reach to 1013. So that's why they mentioned to route same. Here is they are doing load balancing. Again, we're going to discuss load balancing and OSPF. But anyway, SDR, so ten dot, one dot 13 is destination 30 years the subnet mask 110 is the administrative distance. Two is the metric of OSPF, 1023 dot 2.10 dot one. These are the next hop, D3.js, this router next hop, Okay? Then the next thing is the learn this, the time and how they will go to reach to this network. G zero slash two and G zero slash zero. So this interface, and this interface there will mention the interfaces detail as well. So this is called a routing table. The best route will be installing the routing table like an ERP. Now let's move to the second table. So second table is truly about all these things. The second table is the neighbor terrible as the name suggests, they will keep the information up the neighbor, which include the are directly connected route through SPF, their interfaces detail, they are neither id priority, state detailed, dead time or detail and the interfaces. So all the information related to directly connected only, okay, it doesn't mean that they will keep all the detail up, all their outer know, and neither means they are directly connected neighbor. How we can see, let me show you first and R1. R1 has to directly neighbor R2 and R3. So keep in mind it will never keep the neighbor table detail up R4 because it's not directly connected. So one is tonight, but let's see. Let's go to R1 and clear the screen show IP OSPF neighbor. You can see only tonight, but this is the neighbor ID, number ID. We're going to discuss this. The router idea of the neighbor. Okay? Another word, this the, what is called router ID. Then the priority again, we will discuss priority by default is one. And in this state, we are going to discuss this state. So as full and BD are both RBD, it means we're going to discuss the RBD are as well. So forget about these things and this priority, this dead timer. The maximum can be 39 because we discussed the halo packet is 10-second and OSPF and dead time or is 42nd, if you remember from the first slide up OSPF. So they're going to keep the neighbor detail for 40 s. And after 40 s, they will wash out like an ERP. It was different. Yeah, and I show you there as well. I down the interface. So let's do the same thing here. I have a two neighbor, which neighbor I need to down less 35% 24. So this 112, this the IP address of the neighbor. This is the network ID, okay? Nice variety means the router ID. So what I can do, which interface is this one? So let's go to R2 and shut down the zero slash zero interface. And let's see, see the timer. Let's go to R2 and config interface G zero slash zero and shut down. And let's go quickly here. This time will decrease. You can see now 31, okay? And now you need to watch this out because I've done this one is 28 and now it's 23. They're going to wait for 40 s, bring them down. So it's 19 and now it's 17. And now it's 14. Still. Keep them in the library table. And this is the L1 going to wait for 40 s. And now it's seven almost we are nearby, is five, is three, is two. And finally we have zero. And now you will see the message. Here is they said the neighbor dead timer has expired. So this is dead timer, which we discuss theoretically 40 s. Every 10 s, they're going to send Hello packet to find out about the neighbor. So this is for time more, they send them hello. Are you there? Hello, are you there? Hello, are you there? Hello, are you there? Therefore, time is there is no response. So they wash out and if you check there will be one neighbor. So let me bring them back. No shut down. Let's go back. So this was the neighbor table. So dead time or means the maximum value here you can see 39 is 37 because 42nd it will be down, so it will never show you more than 39. This term now is 39, this the maximum one. Now they will decrease. And if they send it 10 s, so it will increase again. Then this the address of the neighbor, the next hop address. These are the interfaces where they are connected to the neighbor. So this was a neighbor table where they keep the IP address of the neighbor interface connected to the neighbor state, either status up the neighbor priority and the neighbor ID. There. Keep these information and the neighbor table almost similar like EEG ERP is mentioned here by the way. Now let's move to the last table, which we call them topology. The topology terrible. They contain the entire road-map like and Google Map. I told you they will keep all the alternative path Aldi calculated best path and everything. All the information, this is called database table as well. And here they will keep not only the directly connected neighbors detail, but they will keep all the information of the entire topology. So in this case, are one belonged to areas zero, but they will keep the detail of area one and area two is well. Similarly, R4 and R5 will keep the information up areas zero and also area of one. So let's go to our four. By the way, either less checkout and R1 first, show the command, show IP OSPF database. As I do Lewis Carroll topology table as well as called database table as well, and Ellis DB as well. So these are all the information they keep here. You see, they say the first thing is my router ideas 111. This is the router idea of this R1. And the process. Process means when we configure OSPF Friday checkout here, show running section OSPF, OSPF one. So whatever you put here, it will show you as a process ID. This one, this one is mentioned here. So this is process ID, and after there, this is router link-state areas zero. And here is, these are the link we call them. You'll remember it theoretically we discuss LSA and LSD and something, yeah. So those things are here. So those things are here. You can see this is called link-state database. These are called link-state database. And what else? This is called topology table as well. And their store everything in this table, which they learn from the entire topology. This table, we also call them link-state database as well. And the entries which you can see here are these entries, like these entries, these entries and these entries, we call them link-state advertisement. You remember we discussed two terminology last time that what is LSD be and what is link-state advertisement? Lsa. We discussed these two terminology, so those terminologies are here, which is fit here. This is called database table. We call them topology table as well. Their store, everything, whatever they learned, and the entire topology we call them LSD be as well. This entire table, we call them LSD be Israel. And these entry, we call them link-state advertisement. Okay. And what else? Yeah. So these are, now let's discuss this is the link ID. This is the advertisement router. Link ID means the idea of the router, again, the router ID. And who advertise all these link-state information. So this is the advertised router. So in this case is similar, but it shouldn't be similar. Some cases then there's the H time the HDMI mentioned, I believe is 360 or something maybe I mentioned. So the h timess, which is 1 h, okay? So there's the edge maximum counter, okay? They will this the edge, and these are the sequence, if you remember on the first slide, I believe you can't remember. I know you'll never watch the video and either you try them. So let's go back to the terminology. And the first slider voice briefly discussed last time. Here is I told you whenever they're going to start from 000001, and whenever there is up there, they will increase this value. This last thing will be seven FF, and then they will start again from 001. So now this time is and who is this one? And let's see any R2. So let's see R2 if we heal because I want to show you to increase this value. So let me find out any router which we are neither like this one. Let's check out this one. So ten dot zero dot, dot one, dot one is me, this R1. I need to look for the yeah, this 11024 dot one. Let's see, 24. 24 dot one. Yes, this one, because they get the highest IP to make them the ID. So that's why 24 dot one is the idea of R2. So this DR2. And what is the just watched part? This one now is b-a. Let me do some changes there, so it will increase. So what I can do and R2, let's shut down something. Do show IP interface brief. If I have something, yeah, let's bring down the 23 interphase. Interphase. Interphase. This one. The one yeah, just bring down any of these. Let's bring down this one so that we notice some changes here. And this should be shut down. Now, if you go back. So you need to watch out here is B. So now it will be C. Let's see how many changes to it. I think so it will become c. Because if there is one changes which will make them see, Let's see now, sorry, Let me show IP database. And here as you can see now it's C if you go just before 24 dot one. So 24 dot one was B. Let me bring back interface. No shut down. So what will it will be become? It will become C. So now it will be d. I told you it will be increased every time. So let's check out again shoe IPO, SPF database. Make them D, It means there's two changes. So D is correctly or sorry, a, C. So now this t, you see it every time it will increase, as I told you here, that the sequence number send update. With every update, the sequence number will be increased. And the last thing they can reach to the FF, and then they will start from 001 again. So they know the entire topology, know what is changed here. So they will check the changes by sequence number. You get the idea. So whenever there is any changes in the neighbors, so they will increase the counter and the counter is 000, 000, and then they will increase one by one with there is or down or whatever. If you add a route, route or do any changes, whatever, they will increase, they will never go decrease. Okay. And then the checksum, the checksum and Link Account link on means how many network advertised by this router. R1 is advertising. So the R2 is authorizing two network. So if I go to R2 and show running section OSPF, let's see how many network advertised by OSPF. So they will count them as a link here, by the way, yes, to why we have three. But the reason is one of them is R1 connected as well. So they never count it when they say no, I have a best route. So they count them only two. So let me show you by the way, this one as well is to link county. Lincoln is altogether okay. It's not separate. Link count means how many link is being. They call them link and OSPF, the network advertised by the neighbor R1 say that I am receiving two network from R2 and they advertise to me that I have these two network to share with you. So S2 here, let me do another one. Let's clear to Lubeck quickly interface LoopBack. Loopback, three-three. Suppose and let me IP address. Let's say to-to, to-to, to-to, to-to, to 55 to 55 to 55 to 55. And let me advertise under this interface, IPO SPF one. You can advertise under the interface as well. And areas zero. Either you need to go to router OSPF and type this command. There is a way directly under interface. You can also advertise this one. I advertise another route, 22 and R2. Before they say that I'm receiving only to link, just to show you that what does it mean by link count? So now our R2 advertise three networks. So there's two should be three. So let's check out the update. And if I say show IP with paved database. So you can see it's now three. It was, the first one was already three, but this was two. So it become three. I hope it's clear and let me remove this one because I don't want to make you confused. So let's say no. And let's go to the interface. No, sorry, the loopback interface to remove the IP. This is the interface and no IP address. And liberate loopback interface. And now let's go back to R1. So this table is clear. This is the topology table where they keep all the information. Okay, so let me clear and let me quickly show you again. This is called database table, LSD, PW, and all these entries is called link-state advertisement. And these are some inflammation which I explained you. So let's go back to our table. Okay. So it's mentioned here as well with detail. So these were the three different table lead you to OSPF, just like a GRP. 6. OSPF Neighbor Adjacencies: The next thing which we need to check OSPF sniper agencies, how they become neighbor. So when you configure OSPF between two router, so they need to go through all these steps to become the neighbor. And every time when they are configured with beer first time. So they need to go through all these process. So before establish a neighbor relationship, OSPF router go through several state changes. The first one is downstate and its state to state X start state exchange, state, loading state and full state. I will show you in the lab you will enable debug to see these state. But these are the state when they go through them. Let's discuss theoretically for suppose I have a two router, R1 and R2, and you just configure R1 OSPF, you just configure SPF in R1. So if you configure one side and R2, right now, there is no OSPF configuration. So this type of state is called downstate, or even sometime we call them if you haven't configured. Anyways, peer find both router, again we call them are downstate. Either you configure SPF and one side, so we call them are downstairs that you just configure one side. The other side is not yet configured. And no neighbors ship is configure this type upstate up with sphere fiscal downstairs. Don't worry, I will show you in the lab. Then after the downstairs, we have entered state here I told you initial steady. But anyway, we call them end state. What happen in interstate? They will receive the halo packet. But the other side, not yet. Anybody sent the Hello packet. They say that any stirred R1 say that I am a router and this is my ID, but I cannot see anyone. They will send a multicast packet, two to 4005. That is there anybody to become an I-bar because we haven't configured anything on R2. So they're going to start to send Hello packet with their information. Don't worry, Hello packet we're going to discuss in next slide in detail. Are one starts sending hello, but still nobody response. So this is called an estate. Once either boys PFS configure and they start to send the Hello packets. So we call them and state. Now after that, we have to waste it in two ways. Now routers see their own router ID from the other side. It means somebody configure SPF on the other side as well. And they also start to send Hello packet. So it means to where to where means both start now hello packet to each other. And after two, where there is x start and x star, well, they will do, they will exchange their DBD. We just saw the database table. They will exchange the summary of their database to each other. We call them X start state. And then when they send the summary of this one, an exchange that they will exchange them with each other. Then we call them exchange state. Even though there is some few thing the select maybe I mentioned here, this is just to tell you quickly and more detail. It is up to date one and exchange state. They will send it. There is some information missing. They will ask those information that might database some of the information or missing. Can you provide me So they will provide and they've been acknowledged as well. So all these things also happen in exchange state. And then they were going to go to the loading state. And finally they will sync with each other. We call them full state. I show you quickly and now let's check out here. The downstate know Hello has been received. An ALU SPF router being in this state means one side, you configure OSPF, but the other side, yet nobody configure OSPF. So this type of state is called downstate because this router is not receiving NO hello from another side. Then entered state, the interface has detected Hello packet which is coming from the neighbor. There's just saw the Hello packets. So this is called an in-state. And to restate when the halo exchange with each other. It means both router now SPF, somebody configure OSPF on both side and they see each other router ID and the Hello packet. So we call them to waste it. Also in the stead, keep in mind, they will decide designated router and backup designated router. We call them DRP, TR. We're gonna see DR. BDM election as well. But their election has happened in their states. Just keep in mind because it will help us when we do this one PRB, DR. selection here is we're gonna do here DR. DR. Selection. So their time, I will tell you that this selection has been done when they were in the third state. To state. Here they will decide who gonna be the team leader and who gonna be the second team leader, the backup team leader. I told you about the ED or BD are in theoretically in OSPF terminology, then x start state, where they will do, We'll begin to exchange LSD be both router will start to exchange the link-state information which did information, this one shoe IPO SPF database. They will start to exchange these information. We call them LSD, be this one as well. Yeah, We just discussed shoe IPSP of database. And also another thing, and this one, they will select master and slave and start state. What does it mean by master and slave? Master and slave is nothing but master means we're gonna end the future. Who gonna send the detail enslaved means we're going to verify, and it means we're going to send a packet first time. Now we're going to be the master and the one with the highest router ID will become master. Again, router ID, we will do a bit later. This one, the OSPF router idea in the next slide. So they will decide master and slave masters. Let me to make the thing simple, because if every router start to exchange information, it will make an issue. So they will decide that, okay, one of them will become master and another will become this lab. Master will send the packet first and they'll slave will send the packet second. Either slave, we verify and send the acknowledgment form anything they're using master and slave. It's like a client server architecture. This is called ex start state into where they choose the RBD or an extra day choose master and slave and exchange the LSD be with each other. Now when exchange state, what they will do. They will send the database Description packet and they will flood all the detail to the other router that okay, I have all these information. Take these information. Now in the loading state, both router has a chance if something is missing in this table. They can ask the other guy that please. I need this one. So n loading state, while they will do, they will, they can do link-state request, link-state update, and link-state acknowledgments. These three things can happen and loading state, suppose before they exchange the Sumeria with each other, summarized version of all these things, they exchange R1 exchange with R2 and R2 exchange with R1. Now both what they do, they compare those things if something is missing. So in loading state, they can ask they can say ls requests, they can request link-state request that, please. I these things are missing. Can you give me the L up there? The other router will give them update and then this router will send the acknowledgement that yes, I received the update. Thank you very much. These things were missing. I request you Update Me and now get the acknowledgment. You get the idea. So these things happen and the loading state, and finally they become sync with each other. We call them full state. So these are the state to become neighbor downstairs, entered state to state X dot exchange loading and full state. Now, let me show you all these things. So what I can do, Let's go to R1 and our topology. And what I can do, let me enable debug IP OSPF, RIP. Oh, sorry, OSPF. And I forgot the command is IPO SPF agencies. And AI enabled debug in R1. Let's enable this one in R2 as well. We're going to test between these two router. So let's go to R2 as well and enable. So by the way, let me go to the topology and quickly show you that I enabled debug between these two router so that we can see. And then I will clear the IPO SPF either first-time when you configure to enable this command, it will show you, but because we already configured OSPF, so we can clear the OSPF so it will become again. And R2 and R1, I want to see all the process. So I enabled DBA guide to SPF urgency. They are true me behind the screen, behind the scene at GNC between you two. Here, I enabled debug and also in R1. Now in one router, I need to clear the process. So it's like a clear the process means to OSPF will start again. So clear I be OSPF process and enter and make, yes. And now you will see the debug to see all the thing which we discussed, the state. Okay, so let's see now the state, so let them complete. And when they become full member and sync with each other, then I will show you. So let them do it. Okay? And then let's see, finally they become sync with each other because now finally there's showing me the full state which we discussed. Now let's go back to the state. The first one is the downstate. When one side EA GRPs configures all the OSPF is configure. The other side. Nothing has yet configure down one side, OSPF ER, so it means one side will be the downstate. So let's go up and let's see here estate down. And it's year as well. If you go down this one, let me make them you because it will show other logs I don't want to hear is the state is down. Okay. So this T Stead because one side is configure, the other side. We haven't received any way SPF this stuff all state. So we discussed this one and now we know that one side, the halo is being sent, but the other side, no Hello has been received. So it's called downstairs. Then init state, they're going to see each other in OSPF packet. So let's see the init state. This is still the downstate, and let's go down and still be the state and still dead stirred, okay? And let's see the init state. So we have to waste your time, should be here, Okay, It should be on the other side because one side should be in the other side. So let's go here. As you see there, say entered state. Cannot see or self in the halo packet that says still I cannot see myself. And the Hello packet, it means they start sending hello. So you can see this is the inlet state and that state is clear. Now going to waste it and to instead now they see each other in Hello packet. Basically they see the ID, router ID in the packet. That's why they mentioned here, there's my router ideas, There's one, but I cannot see myself. But in two-way street, they see each other. So that's why they call them to waste it and do instead, we saw that they will choose the RBD is well, let's verify two things to estate and also DRP TR. So we can go to either router and the after the init state to state. So to start as done. And they said, Let's elect a B D, a B, or B, D, or election in which one, and the two estates. So this we say they tend to wasted, they will choose DRP, DRP as well. So they say Let's start through the election of DRP ED or BD R11. One S means this router become DDR and ten dot one, dot one, which is our two highest IP. So they become the DR, so R2 and R1 become DBDR. Here they mentioned, and to waste it, that we've done the election and I lost the election, I become DBDR and the router to become the DR. Because of the router ID, the highest router. So this one is done. Yeah, so this was to waste it, which they see each other. A two-way communication has been done between these two router. Now let's move to the other one, x start state and x star. They will begin to exchange the database with each other. Whatever this router has, they will exchange with the other one. And also they will choose master and slave. I told you what is master and slave. So let's see in master and slave. So after two where we still two-way. And let's go to, here is, Let's start here. Let's start x, start x, start. I told you they will do a communication related to V are the slave. So R1 become the slave because low router ID. So again, who gonna become the master? So R2 is master. Let's go to our due date will be mentioned we are the master. Let's go to the start. And here they say that we are not the slab or 2M naught the slave. And he said, I'm the Master. We are the master. Our to become master because of the highest router ID, because this DBDR R1 and he is DDR. So due to DR, because you gotta highest router ideas. So definitely he will become mastered as well. So this state x start state, they do two things. The first thing is they will exchange their database. Here is first database and we're not slave. Let's go to our one. Here is they say because he is the master, so they will receive the database. They received the database, and they become the slave and the other side become the what is called the master. Also, it doesn't mean that they can not send. They will also send the database because we discussed it, extract they will start to send the database, okay? And after that we have exchanged state exchange. They will start to share all the information. So after extort, there is exchange. Third here is exchange that they received the database and the flood all the information to the other neighbor. And finally, we held a loading state and loading state in case something is missing. So they can go through all these three process link-state request. The router will link state update and then they will apply them, sorry, reply them with the acknowledgment. So let's see unloading state. If something is missing, this is a loading and the loading state. Okay. Let's see if the LSA account and they get all the columns so they have one request, anything because it's not the first time configuration we clear the process. So this is the loading state. And the loading state, by the way, they're synchronized so they haven't ask them anything by the way. Anyway in case if for this first time, so they will ask them. And finally we have a fully stirred and they become sink and they have the same database. So all router has the same database table, which we'll call them topology table as well. So that is called the stateful. And here is the synchronized with each other. So these are the OSPF night but agency. Okay. So we're done with this. And then we saw from the debug command, so downstate and instead and to estate, they become established night but urgency and this state and then the other packet from x start to exchange and then load into full state a base distilled spirit database, which I showed you previously. So by the way, these are divided in two categories. The first one, they tried to become libor, and the last 1234 packet synchronize their database. This database, all the router has the same, this database, this topology, if you go to any route and they are all, we'll keep the same detail because like a Google map feature I gave this example before as well. That's it. This was OSPF night, but urgency how they become neighbor. And these tips are mentioned here as well. And I show you practically as well. 7. OSPF Metric Calculation: Like it, yeah, GRP, GRP metric. And it was a long formula. Anyhow indicates upwards is so easy. Ospf use metric called them cost. And cost is, by the way, is nothing but a reference bandwidth and divide it by the interface bandwidth. One way or another way. Things are going to the bandwidth up the interface like EEG, ERP, anyhow and AGRP, they were using delays. Well, here is no such delay. It means cost is indirectly the bandwidth up the interface. If we check out this formula, is z reference bandwidth and divide it by the interface bandwidth. And it will give you the cost of the interface. And Cisco, the reference bandwidth is 100 megabit per second. Either we call them 100 megabit per second or ten to power up eight. Simple as 100 megabit per second, which is the color pondered megabit per second. This reference bandwidth, by the way, and other vendor, it can be different. How we can find out this reference bandwidth. If you go to any router and type here, show IP OSPF. And if you go down, it will show you the reference bandwidth which is used right now. So here is they say that the reference bandwidth is reference bandwidth unit is 100 megabit per second. That's what I told you. In Cisco, the reference, but what is 100 megabit per second? So the formula is so simple. Peg the reference bandwidth, which is 100 megabit per second, which is mentioned here as well. And divide it by the interface bandwidth. Suppose what is the interface bandwidth in this case, suppose if I check show interface G Z roughly zero. So the bandwidth of this interface is this one, but this is in kilobit per second. So I need to change this to the, what is called the megabit per second because the reference is in the megabit per second. Whereas the reference I just show you this one. This is 100 megabit per second, and this is something kilobit per second. So you can easily change this one. If you go to Google. Kilobyte to NB, there may be many calculator. By the way, you can go to any calculator. And just this is an kilobyte around. Either way, it will not show you the correct one. It's 976 doesn't mean this means the hundred, not 100. So it's 1976, so 100 years, so it is equal up 100. So it means this is 100 and this is 100. 100 by 100 means my cost will be one. Yeah, so simple. So the formula is too easy. So the reference bandwidth, I have 100 mbps and the speed of interfaces right now is 10,000 kb. So I convert 10,000 kilobit to what is called megabytes. So it gave me 100, 100, 100 divided by. So here I can type show IP OSPF interface. So here I will see the cost is one. So the cost is one because it's divided by, so it will give me the same. Either you can find out from here is we'll show IP what is called Shoe IPO SPF in here. If I say section cost, cost maybe in small letter. Should I be OSPF interface and Section cost. So we can find out from here as well. So this the cost of one because all my interfaces or gig. So it will give you the same cost just to tell you, show you. So it is a simple formula. If more than one destination has the same cost, so they will make a load balancing. Load balancing we will discuss like an ERP. But anyway, this is just to tell you. Now, this is the simple way. If you have an Ethernet link, right now nobody is using Ethernet link, but anyway, you have Ethernet link. So this formula will give you a cost of ten. And if you have fast Ethernet link, so it will be one. If you have a serial link, link is also not anymore. So it will give you 64 and rest of all the interfaces. Gig 1020304000 gig, whatever. All of them are equal to one. Because when they introduce OSPF, there wasn't no debt in the future, the interfaces will be changed from Ethernet to Fast Ethernet. And from first two it will be gig and ten gig and 4,000 gig will come. When their time they decided that the normally and dose only Ethernet link was there and serial link. That's why they make this formula that the Ethernet will give you ten cost and see the link will give you 64. However, because later on now the interfaces or change the bandwidth as high now, this formula will give you 11 for anything gig or ten gig or 20, or 30, or 40, or 50 or 60 or 100 gig, whatever. Yeah, you can change this if you weren't. Suppose user know what the **** is this. If I have a ten gig, again, one cost, if I have 40 gig, again, one cost, yeah, it's okay. You can change this reference bandwidth. You can set your own. You can go to router OSPF, and outer waste P of one. And I think so I forgot the command costs something, no. Ospf reference cost or something. I need to check the command but it's there. So let me quickly see if I remember your article. Sorry, I remember R2 cost. And here is the reference bandwidth. So the reference bandwidth is right now 100 megabit per second. As mentioned that you need to put in megabit. You say no, and my network, I have ten gig and 30 gig devices. So change them. Then. They say you need to put this in all the routers. So now the formula will give you a different cost. And maybe if I check their interface, now let's see. So the cost will be ten. Now, you see before it was one, now they make them ten because I changed the reference bandwidth. Anyway, let me reward, because it can give you wrong information as well. If you change them too much. So you need to be careful what you need. So you can change the reference bandwidth. It's up to you. What else? Let me change to give you, what can give you the reference? Suppose I give them much. Sorry, One more. Okay? Now, if you check, let's see the cost. Okay? So it makes them thousand. I need to increase more. So they will give you a wrong value here. Okay, it is not far, this one, sorry, it will not give you four gig. It will give you for Ethernet and serial link. So if your network, if you have Ethernet link somewhere, so it will give you a wrong, the wrong information. So it's better. Change them. If you know that all your interfaces are in ten gig, 20 gig, 4,000 gig and you want to modify the formula, so yes, change them. However, you don't need to change the default reference bandwidth anyway, let me make them different. One, show, I saw the router, OSPF one and let me okay. Let's see at one or not because I want to make them you have to use the cost. All of them is one now because it's the hundred one. This the shortest way. So you don't need to, if you have a gig interface to consider, your cost is one. So all my interfaces or gig interfaces, that means my cost is one. I do need to do the formula, but anyway, I'll show you how to find out. It is so easy. You have a reference bandwidth, which is 100 megabit per second, and you can find out your reference bandwidth. I show you show IPO SPF, and it will show you the reference bandwidth divided by the interface. If their interface bandwidth is not in megabit per second, you need to convert them to megabit and it will show you the value. I gave you an example here. The reason is they will count the outside interface cost. So suppose if you have a topology like this, here is fast Ethernet, Fast Ethernet, Fast Ethernet, but here I have eaten it. We just check out the Ethernet will give you ten. So now if you go from PC1 to PC2, so this way it will take a twelv cost and the return three cost. And even though everything is same, the reason is it will come the outside interface. So when the prophet go out from R1, so it will count this interface, not this one. Here is the cost is one. Here is the cost is one, but n, it will enter through the exit interfaces, this one, because this is an Ethernet, so it will bless them ten, because Fast Ethernet is one facet and it is again one. Ethernet is ten. So that's why from this side is give you a cost of 12. But the return traffic PC1 is sending, so it will not count this one. The exit is this one. So zero slash one is fast Ethernet cost 10 plus zero is fast Ethernet cost one. And exit from here. So zero slash one interface cost one. So this R that will give you a cost of three. So in the routing table, if you remember, those, 2.3 is basically this value. I hope so now you get the idea. If I check show IP route OSPF. And here you see the two. It means this is the cost and here is three. So this is this way. It will show you three because it does depend on the interface bandwidth and divided by debt and then they will give you the cost. So easy formula to find out. Okay, so now let's see in our topology, let me quickly show you by the way here, the routing table. In our case, we have also three. And then I will find out the interface caused by this command, the exit interface, and we will place them. It will give you, like in this case, I need to find a route from R2 to R1 to reach ten dot one dot 13. So I have two possible where to reach when I check out. So they've given me a two-part. If I go to R2 and you are, let me disable the debug and show IP route or SPF. So they told me that if you want to reach to 1013, I have two-way. Let me copy this one. And we need to find out why they are showing us these two. Let me take this one here so that it can, here is, you can see there's two. This is the metric I told you. I will show you now how they giving this to. Let's go to R2. R2. Say that if I want to reach to tender 13, my cost will be two. And also from this side. So let's find out. So R2 when the traffic is going out. So they will check this interface bandwidth and cost. So this is a zero slope zero interface. Let's check out the cost of zero slash zero interface when the traffic is going out. Sure. I saw the show interface. G zero, slope zero. So what is the bandwidth? Bandwidth is this one. Okay? Let me put here this is G zero sleep zero because they will only check the outside interface bandwidth and divide. Next thing When the packet goes out. So the second day we'll check this interface to reach to tender 13. So I need to go to R1 and find out G zero slash one. So let's go to R1. You want to do a same, but just to show you that so that you can get the idea. And G zero slash one. What is the bandwidth update one is same. So by the way, let me type with KP because this is in kilo bit. So I need to change them. So G zero slash one, the outside interface is this one, That's it. And then I will reach to the destination. So to exit interfaces are coming. First, I need to find out the cost of this one. So the cost formula was so simple. And the cost formula say that there is a reference bandwidth, whereas they're referenced bandwidth, which is 100 megabit. We ended that mentioned. So you can find out that one and show IP, OSPF and R1. Suppose somebody asked, you know, show me where is this? Here? This is the reference bandwidth. So this is the reference bandwidth, which is 100. So I need to divide 100 by this IP first, it does this one, but this is in kilo, so I need to convert this one first. So I type this one, it gave me 100. So let's go back. So the equal of this one in Saudi and megabit is a hunter and also equal up this one is hundred. Now formula say take a reference bandwidth, okay? So this is the reference bandwidth divided by the interface bandwidth. Interface bandwidth is also 100 equals one. And similarly the other one is 100 divided by hundred. And then one. And then finally they say, bless them. When you reach here, here, here and here in my case, I help only to reach this one, cost one, and class two. So what is the value plus these 21 and plus one equal up to? So that's why it's showing us here to get the idea. So this is called cost. So if you go back to R2 and if you go to routing table, so you will not be confused this time. Similar like an ERP. We find out the value this time we found out the OSPF metric. So if you see two after this to you not to be confused. Now you know how to find out this one. Here is mentioned three. So definitely if you want to reach to 17230, this is in r2. Here is 172 to 30 years cost one, here is cost one and should loopback interface as well. So that's why it's showing us here three. So you don't need to be confused because we have a shortcut as well. No need to divide. I just show you how to divide too. Because if you have a gig interface, just type 11111 and how many giga are coming, just Plus them and you will get the car. So, so simple to find out. This was the metric, I hope so you get the idea. By the way, you can find this to buy another way as well rather than to place them. So which interfaces coming? This one, yeah, the first one. You can do one more thing. Sure. Iep, OSPF interface G is useless zero and section I told them only show me cost. So the cost should be capital. Here is, they said the cost of this interfaces one. And now in the way there is another one is also coming R1 interface. So type the same thing, but change the interface. So let's go there. And G zero slash one. G zero slash one. What is gear? Show I post BF interface, okay, costs should be capital here is one, N1, make two, so that I can reach this standard 13. And that's why in the routing table is two. So you can find out by this, we don't need to divide the division. I just show you how it is work. And now you can use this one, this show command to find out as well. We find out this one that from where these two are coming and we check out from the interface, exit interfaces as well. And you have the bandwidth, the bandwidth up the interface, and you can divide your own to find out. And also if you want to check out the reference bandwidth. So the command is shoe IPO SPF, and here it will show you the reference bandwidth. I told you you can change the reference bend to it is well, under the OSPF configuration, if you are not comfortable with this one, this value is not good for me because all my interfaces are in ten gig, 20 get 3,040.50 gig. And it doesn't make any sense to give me 11. So you can change them so it will give you different value and the formula will be changed. Okay? So definitely the path will be changed. Then the best route will be changed. 8. OSPF Packet Header & Types: Next topic related to OSPF is OSPF packet types, different types of OSPF. But before going to OSPF packet type, we need to check OSPF header because you're going to find these OSPF packet type inside OSPF header. Let's see the header information up OSPF. This is always p of header. And this was pure filter. We have a version number IPV4 or IPV6. And we have protocol number 89, which is spatially used by OSPF. I told you and the theory part, if you remember, I told you they are using port number protocol numbers are in art board is protocol number 89. Then we have our packet length, router ID area already, checksum, authentication, authentication type, and data. Insert this OSPF packet when you open them, but this is the header. And insert. We have so many information. When you open this header, I will show you in the Wireshark, don't worry. But here you can see the version one Jen for IPV4 or IPV6 is for IPV4. And version three is far the IPV6, then the router ID. Then we have area already at 00, either one ADR or two or whatever type. With PDF packet type, it is a halo packet or database description are acknowledgement packet. What are these information linked up the packet checksum, the of the packet which I showed you from IPO SPF database. Authentication if you enable authentication. So they will show you authentication type. It is a clear text, either md5, an area is zero, or one router ID, which is the highest IP address, either the loopback interface. So all these information is inside the OSPF packet header. Don't worry, I will show you. You're going to find out OSPF origin to because right now we are running IPV4. And the message type, you're going to find the OSPF packet 12, 345. These packet one is a Hello packet, and then we have our database descriptor packet two. Then we have link-state request packet three and link-state update packet four. And we have link-state acknowledgment packet five. You're going to see these packet. Insert the message type up. The header row is P of hidden total length up with SPF packet, the source OSPF router id, the id which areas belong to 32-bit area idea it should be 000, either one or whatever. Then the checksum, which is the hash value and authentication. However, our main target is OSPF packet type, which is inside this header. And those packet are Hello packet, Database Description, link-state request, link-state update, and link-state acknowledgment. We have five packet and OSPF. These five packet are inside and the OSPF header. So it's better to show you this OSPF header first, which we discussed here, this one. So what I can do, let me capture any of these router by Wireshark. And if I go to G zero slope zero interface to capture and Wireshark, I will show you the header, whatever we discussed. And then one-by-one, we will discuss the packet type and then we will see in the Wireshark practically. So let's see to capture a G zero slash zero interface up R1, which they are receiving OSPF detail. So let me capture. Just give me a minute to start. Some term is not working. Let's see here. Let's see type here, OSPF or SPF. And here it is. So let me, I don't need this one. Okay, I'm interested in the header. So let me, we already know two to 4005, this D multicast here. And this is the halo packet after every 10 s they are sending. So let me open, Open Shortest Path First. And this is the wispy of header. And now this is the USB fader. So let me zoom it. If you can see this is where spear feeder we have a virgin information version two means we are running IPV4 and these are the message type and message type. It will change. It is, it should be one, it can be two, it can be three, it can be four, and it can be fired. And the message type, we have many packet type which we will discuss in the header. Those packet message type will be showing here those packet like a halo ****** descriptor. And then the other one, database description, and then link-state advertisement, link-state request, link-state update, and link-state acknowledgment. So you're going to see all those and the message type, then the packet length, this is the length of this packet. Up the halo packet, then the who is sending this one? There should be the OSPF router information. And this is coming from areas zero Enter to do, but it will show you this area and it's coming from backbone area. We discussed this one. This is the checksum. There is no authentication enabled. That's why it's showing zero and no authentication data because you are not using any type of authentication. So this is the header information which we discussed here. So inside the header, it will show us that the header is IPV4 or IPV6 message type, which type of message header is taking? It can be one to five. Right now it's showing me one, then the packet length, length up this halo packet. Then from where this packet is coming from, which area is belong to, what is the hash value and desertification enable or not. This is OSPF header. Okay, so now we know the USP of header. So let me update message. You'll see this will change. You see four, just before it was one year, message type will change and Hello packet is, is one. And NSA acknowledgment, you see a swipe. So they will change them anywhere. We will see those picket as well a bit later. But you see now the header information and all these value. Now you get the idea there was version two for IPV4 and type was the halo packet. It can be a DBD, it can be LSR, LSU and acknowledgment. Then the packet length, which account then the router ERD AT or D was zero V checkout. And then the authentication type was null because nothing is configured and there was no authentication and we saw the checksum as well. Now you get the idea that what is the OSPF header? Now coming to the packet type, we check out all these things. The first bucket is hello. So let's discuss the Hello packet. Hello packet or OSPF type one. You see this two type one because there are five different types of packet. The type one is the halo packet and it is a multicast periodically send by 224005. All the interfaces which they are connected. They are using this hello first time to make a neighbor ship. If you remember, just before any agency visa there, the first Pickett was hello. So they are using this halo far neighbor sheep as well, and also to maintain the neighbor shape. When I shut down the interface. So they say that I read for the guy 40 s and it's not anymore. Who found out by hello packet for time is the halo go there and no response. So they shut down their interface. So it means first time they are using for our neighbor ship and later on they're using for our maintenance far maintain the neighbor ship. They are using this Hello packet for Neighbor Discovery. And also far keep alive or keep alive means they will check continuously did the neighbor is available or not. They are using first time for many other things as well. So this is type one of the packet up OSPF, Okay? And now in this packet, in the halo packet, you will find many things. Ospf word gin, type one, packet length, router ID, NTID, checksum, authentication type of authentication data, network mask, hello interval, dead interval, priority, network ID, the RBD or FDR is in case if there is, then router ID and also stopped flake and many more. All these information you will find in the halo packet, it is a small packet, but they will keep a lot of information. This Hello packet is used mainly for two purpose. And as I told you, you will find router ID, hello interval, data interval neighbor ID, area ID, authentication, network mask. Area can be any area normal. Right now we have a normal area and also DR. video and priority. Let's check out this Hello packet. Does it keep all these information and they are using for which purpose? So let's go back to our lab and let's click on Hello packet. And let's go to the Hello packets. So they are using Halo ****** two to 4005, which is a multicast, is cleared. And let's open the halo packet. It's here. Insert the header. There is a Hello packet. So I open the Hello packet and let's go to zoom it to see this is a Hello packet. The first thing I told you, they will keep the subnet mask retail. They say the guy who I'm connected there subnet mask is 255 to 55 to 52. Yes, this is what we configure. Then the halo interval they say is ten second, yes, there's the halo interval. Then they will keep many other information as well. This is the priority router, priority is one which is the default one. Router dead-end terrible is 42nd. Hello, interval, ended interval. They say their DR is this one. I do do they will keep DR and BD or inflammation as well. They say they're DR. the team leader is ten dot, dot t2 and bake-off designated router is ten dot, dot one. So backup designated an active neighbor is 111, which is R1. So you see a small packet with the size up 48, okay? And by the way, this message type is Hello packet one. And they keep all the information like area already. Router, IP, packet length, authentication information. Authentication. We don't have authentication. And then I told you they will keep network mask, hello interval, dead interval, and then router priority, router dead interval, DBDR. So all these information is being exchanged with the help up Hello packet is done and you check out the Hello packet. Let's move to the second packet is database descriptor packet, which is a type two packet. Hello was one. They're using this message to synchronize the database. And we check out the database. You'll be Shu IPO SPF database command. We call them LSD B is where link-state database. So they're using this database descriptor to exchange information with each other. The summary of all the database. Using for this purpose, somebody up LSA and LSAT, I told you already and they vertically Let's see this one and what else will be? So they will carry the database information and they will exchange them are same copy to the neighbor that I held these information. And by the way, database descriptor is in the xt start state. You remember extracts, did I do there? As we'll see, they will exchange the summary of the route so as here as well. Okay, So how we can create this database descriptor, I need to change something. So what I can do. And R2, let me clear the process, clear IPO, SPF process, and let me make them. Yes. And let's go back there. So here the database descriptor, let's see, here is this the database descriptor? And it is inside the OSPF editor, which is the type to this what I just mentioned too. Let's open with prayer of database descriptor and open here as well. Let's make them a Zoom soon. As we can see. Here, we have database descriptor, which is our type two packet message type is type two. And OSPF database descriptor. They will exchange the route information and the route information also here they will choose the master and slave as well. So that's why they are mentioned here as well. Okay. And what else? Yeah. So they will start to exchange the LSA and it should be somewhere here because our two has many things, so I don't know which they exchange. So it's not mentioned lead capture, another one, database descriptor, maybe another one. They start to exchange here as we have another one. And I need to see the route which they exchange the database table. So let's see not this one. Yeah, So here is the exchange. All the roads, you know. And if you open all of these, whatever r2 has, the exchange them, they are what they are, these are the information. So they will exchange them that they advertise router R1. And then let's see what they give them. They'd give them whatever they have one-by-one. Here is all the detail. And the database. Which database you IPSP of database. So let's see, open all of them. So they give them 1035 pays well, and they give them 1,035.1 cell to 230. And all those ones I want to to 38 the other 13 Israel for all the information they give them because in this state, they will exchange the DB database. So they exchange them because they clear the process. Next is a link-state request packet, is the name link-state request. Link-state request is OSPF packet type three. Type three because we have fiber type. And link-state request packet, is if something is missing. So what they will do, they can request them from the neighbor. That okay, You give me all the terrible. But I checked the table. There is few things missing which is not up to date. Can you give me this update? I'm requesting you please give me the missing information. So let's see if I hail. Otherwise we will create such scenario. So link-state requests here is S request. Let's see. Request number three, sorry, the packet type number three. Here I say link-state request. So this is a type three and here is the link-state. I don't know which thing they asked them to provide us. So the router may ask them some information. They asked him information about 10:24. They asked them information. They do have the information of 1024 when you were down. I missed this update. Can you give me information obtained before I'm requesting you rest of the thing and my table. I already ****, but these things were washout. Can you give me update up this 1.10, 24? They request them link-state request. So now in the response of LS request R2, what they will give them, definitely they will give them link state update, packet, link-state update. Either LSU packet is type four packet link-state update. This is the reply up link-state request R1, request them dead in my table. Ten dot Sorry, what was the tender? Or ten? One dot 24 is missing. Can you give me update, update one. So here is LSU update. So these are two will reply them. So k here is update, which is a packet type number four. And they give them the information of these route which was missing tender 24. So they will send up there too. Okay. No worry. Here is the update. So they will give them the update, okay? So they sent them the update. And finally, R1 has to reply. So R1 will reply that link-state acknowledgment packet, which is the last OSPF packet die five. Okay, thank you very much. I get your update and let me acknowledge view that I get everything and thank you very much. So this is called link-state acknowledgment packet. And if we go back, so definitely when R1 results, so they need to acknowledge here is LSA acknowledgments. Here is LSA acknowledgment, which is the last one I fight. They will send acknowledgment to the R. Do that. Okay, I get your updates and now I synchronize my everything. That's it. So this was the link-state acknowledgments. And you can capture I told you in shortcut, but I hope so. You get the idea. If we go back and let me quickly revise the halo packet, take many information, such as the USP of origin, packet length, router ID area, the checksum authentication type, network mass halo interval, dead interval, priority, neighbor ID, the RBD or are those information they are keeping their use Hello packet file to purpose. Periodically they are sending after every 10 s to keep alive. And also for our network disco the first time they're using Hello packet. And then we check out database descriptor packet, which is happening the start state. So they will exchange these summary of the route, whatever this router has, they will exchange with the other one in the database detail with each other. So they are using this packet type for database exchange. And then finally, we have three other type. One is link-state request packet. If something is missing with one router. So they will send link-state request to the other router. I don't have this route information. Can you give me the other router will say yes, I help. Let, let me give you, this is called link-state update. And finally the router, which request they will send an acknowledgement and that's it. Those are the OSPF packet type. 9. OSPF Router ID Selection: Next topic is OSPF router ID. Either ID. Basically router ID is a unique identification. I told you like in your home or house, you cannot give the same name to you or to three brothers because it's not possible how you will do communication. So the name has to be different. Either in the same network. You cannot give the same IP address more than one device because there will be conflict. Similarly, an OSPF, also, an EA GRP Also and BGP protocol. What they do, they're uniquely identified by a router ID and those router ID hesitant to be the same, otherwise they will give you an error. And my network suppose if I give the same router ID to R1 and also same router you to R2. So they will give me an error. Who SPF will start to give an error that the router idea is same and hasn't to be the same. So basically this router ID as a 32-bit long, the number same like IPV4, but this is not IP address. It is same like IPV4, but it is not IP address. But however, the IP address has to be the router ID. But don't consider them that the IP address is the router ID. No. Router idea is similar like an IPV4 address. Now, how do you choose this router ID? Because you see an every OSPF when they're due communication show IP OSPF database. Here they're showing me that my router ideas, this one everywhere they are showing router ID. Here is also link IT. And if I go to any other places, well, they are showing a router ID. It means when these devices doing communication with each other, they're using this unique ID to communicate with each other. So you need to give unique ID, which hasn't to be the same and the topology. Suppose if I give the same tuple ID, let me give them the same to show you the error. Suppose and R2. I go to router or SPF one, and I type the router ID. Suppose 1.1.1.1. Okay? And let me clear the process. Clear IPO is P of process. So they can take the IP address and let's see now they will start the error. When they do the UC, they said detect duplicate router variety. They said this ID belongs to R1. Let's see, here is also the era show IPO is PIR database. This router ID belongs to R1. They will never become night, but this is one of the condition. So I need to change this IP router, this router, router, OSPF one. Here, I need to type router ID supposed to D2, D2. And let me clear the process so that they're not chewing error. Now the error will go. There is our duplicate error at me. This shouldn't be the same. Now how do I choose this router idea and how we can assign this router ID. The first thing is, you can assign men will just show you a second. If you haven't assigned, they will take the loopback interface, the highest loop, loopback IP will become the router idea of the router. And finally, if there is no loopback interface, then they will take the highest interface, Ip will make them as a router ID. So here I choose a man Willy, this router show running section, or SPF. Because the neighbor was down because of the router idea to leave, they will never become neighbor. Here I type a manually. So if I go to configuration router or SPF one, and here is the router ID and question mark. So the router ID, they said that OSPF router ID is in the address format. So I can give them two to 422-422-4522 for support. And one is taking this IP, it means it's not the IP address, but a same IP address. Just to tell you deliberately I type this router IT. So I should clear you this is not the IP address, but it is in the format of IP address. Okay, it's clear. First thing is if you want to give IP address to the router. So one way is to assign men willy, they will take their type, not that IP, but that router ID will be the router ID of this router. Meanwhile is the first 1 s one is the loopback interface. If you are not configured manually. So here is this R4. We have many Lubeck interfaces. But in R4 maybe I already configured manually. Let's see shortening section. Ospf. Let's see if I configure manually, I will remove meant really to see how they will choose the router ID one way or another way there has to choose here. Here I never configured, you see, I never configured manually. There is no router ID, but they choose router ID. What is the IP or the, what is the route ready? Let's see. R4 show IP OSPF, OSPF database. Let's see, yeah, 172 to 168, where this IP come show IP interface brief. Let's see why they take 172268. These are all the interfaces. This 192 is the highest one, but then never choose the physical interface IP. They choose the loopback highest IP, which is one cell to 21681. So this point is clear. First I configure and manual. You can give them the lowest IPS. We'll take it, we'll take the lowest router ID if you configure manually. But if you do not configure manually, they will choose the highest loopback interface, IP if Lubeck is available. So an R4, Lubeck is available. The highest Lubeck is this one. Why they choose? Because Lubeck will never down until the router is down either these interfaces men will it down by administrator. Because this is a logical interface. And this was a physical interface. It can be down anytime, so it will down the process of OSPF as well. So that's why we SPF say that I will choose FOR loop back is available. I will ignore the physical interface. Even if they have the highest IP, I will choose the Lubeck highest IP done. That's why they choose. Once I went to 2168, which is the highest one. If there is no physical and suppose if there is no loopback interface, the case of R3, Let's see show running and see if I did not configure router ID. So then I can show you, let's see, show, show running configuration section OSPF. Here I did not configure. Now there is no loopback interface show IP interface brief. What do you think which IP they will choose? Definitely they will choose the physical highest IP, in this case, ten dot 135 less checkout show I view is PDB database and here is ten dot 135.10 dot one, dot one. Because now Lubeck is not available. If Lubeck is available, even if it is below IP, they will choose that one. So these three things are clear, how they choose and how they select the router ID. So the first one is manually whatever you set, they will take that one. If you haven't configured, then they will choose the highest LoopBack. Loopback is not available. They will take the active interface IP. The command is router ID. I'll show you. Here I choose and I show you a different one. This domain wall on which configure men willy and R1. That's the command. And then reduce your IPOs, be able to see them. And then the second one is, if you remove this IP, they will take the loopback interface IP. We saw that one as well, but you need to clear the process. And then the other router, we check out that they take the highest physical interface or API and R3. And then finally, I show you that it doesn't mean that this is the IP address deliberately or type two to nine, which is not the IP address. And then 229.2 to nine and a steak that one and that one become the router ID. So this is called router ID. This concept is similar and ERP, we haven't done it yet ERP. So the same process can be applying an ERP and the same thing can be applied in the ear or what is called BGP as well. So all these three protocol choose router ID, which is a unique number, same like IPV4. And then I choose the same router ID, so it gives me an error and the neighbor shipped down. Then I changed the router ID so they become night. But again. 10. OSPF Different Router Types: Next topic related to OSPF is a router type. Ospf router type. Basically OSPF utilize different type of routers and explain different roles and different location in OSPF domain. It's like, you know, let me tell you before. There are four types of OSPF routers. We are talking about Router, role, different type of OSPF routers. So basically there are four types of OSPF router which played different roles, different function on different location. To verify which type of OSPF router it is. So we can use a shoe IPO SPF command. This command will tell you the roll-up OSPF. It can be ABR, it can be HBR. We discussed these two terminology, area border routers and autonomous system border router. And it will tell you that the router is internal, either backbone router. Again, we discussed these two terminology as well. So now it's also possible that a router can be more than one role. Maybe the router is ABR as well and it is internal Israel. Just giving an example, maybe R outer is ABR. It may be a backbone router as well. It's like, I am my father, but the same time I'm a son of someone. It means I'm playing two roles right now. I am a father as well, but I am a son of someone as well. The same way router can play more than one role is really just keep in mind. However, there are four different types of OSPF router. So suppose in our hear this topology, this R1 player roll up ASB or we will see I've just showing you I already right here. And this R2 and R3 play a role up ABR area border router because it's connect to different area. Also are three also connect area to area zero. To connect area 12, areas zero. As we discuss theoretically and previous OSPF classes. These terminology that what is ABR and what is a SBIR. Also, this R4 belong to the same area. All the interfaces belong to the same area, which is area one. Similarly, R5 belonged to area to totally. However, this router one interface belong to area 1.2 interfaces belong to a real zero. Similarly, R3 to interfaces belonged to areas zero. One interface is an area too. Just to explain you the things. So every router play a different role, which we will see. However, there are men for roll up the router is BR, ABR, and turn the router and turn the router and area backbone, either backbone area. This is called OSPF router type. The first one is N-terminal router. And turn the router. All the OSPF interfaces belong to the same OSPF area. This type of router is called Internet router. And this type of router has a single state database because this interface, this already, this router belong to only one area. This way they will keep a single link-state database. We discussed stead. Link-state database is well different. Ospf payable. So one of them will discuss database table is if you remember, I hope so. This type of router is also called adjacent router, either adjacent neighbor. So the router will be called internal router if all the interfaces up the router where you configure SPF belong to the same area, then we call them internal router. So what about an hour topology and our topology, if I can see, so R4, both interfaces belong to area one. Similarly are five. Both interfaces belonged to area two. However, I cannot say internal router to U2 because U1 up the interface belong to area 12, interfaces belong to different areas zero. But in another word, R1, all interfaces belonged to areas zero. Anyway, we will see a bit later just discussing theoretically, this is called internal router. Now let's go to Backbone router. The area zero, which I do a scale backbone area. And the router which partially belong to areas zero is called backbone router. What does it mean? It means if the router interfaces, either some of the interfaces belonged to a zero. So the router is Carl backbone router. So let's go back to our topology again. We will verify a bit later, don't worry. So in our case, are for both interfaces belonged to area V1, R5, both interfaces belonged to area two. However, R2 and R3 are the two router which partially belong to a zero because two interfaces or R2 and two interfaces are three belonged to areas zero because we advertise these two interfaces and these two interfaces in areas zero, while this interface in area one. So R2 and R3 article backbone router as well. Even though all the interfaces not belong to areas zero, it's okay. But partially is belonged to areas zero. So we can call them backbone router. Similarly, R1 is called backbone router because all the interfaces belonged to areas zero. You get my point. Okay, so now let's go back to it. Now you know the backbone router, the router which partially belong to areas zero, either one or more than one interfaces has been configured in areas zero. Because R2, if I go to R2 and R3. So let me show you, by the way, if I go to R2, show running configuration section or SPF. So two interfaces, area is zero. You can see this too. We advertise these two network and areas zero, either I, if I say show IP interfaces. So two interfaces of this router or an area zero, this one, and also this one. There should be another two interfaces as well. One interface belonged to area one. Here is these two interfaces, G zero slope zero and G zero slash two. These two interfaces, G zero slash two and G zero slash one, belonged to a real zero. So such type of router is called a backbone router. Now going to the third one, area border router, area border routers, at least one OSPF interface belonged to areas zero, and at least one interface belong to non big bone area. I told you other than zero is called land backbone area as well. And we can verify it by this command. We will see a bit later. And also ABR is a router which maintain multiple link-state database. The reason is it's connected to different area. And this is a router where we do the summarization. We will do summarization a bit later. But just keep in mind, the summarization are not done on any router. It's not like ERP or RIP so that we can do summarization anywhere. No. Summarization are only done a few routers. One of them is area border router. This is the router which maintain multiple link-state database is one interface. It leads to connect two areas. 0.1 interface connect to different areas. It can be area 1234 and so on. And we know that area border router, the router which connect different network area. We call them Area border router, or another word area border routers, router which connect different area to area zero, we call them Area border router. Now let's go back to our topology. Here. R2 and R3 are the only router which connect area one. And this side they connect area to area zero. So these two router play roll up area, border router, which connect multiple area with each other. And it meant and multiple. Database, link, link-state database. Okay, Done. Now let's move to the last, which is autonomous system border router, a SBAR. Sbar is the router which one interface connected to OSPF domain and other interface is connected to any other protocol. It can be raped, it can be AGRP, it can be BGP, it can be IS-IS, it can be anything. Again, this is a router to which we do the redistribution. This is a router where we do the summarization as well. This is a second router where we do summarization and OSPF. Again, I will explain you there and OSPF or summarization. But anyway, just to tell you, just remember autonomous system boundary router, what they do. They exchange information between external routing protocols such as EEG, ERP, BGP, RIP, OSPF, OSPF detail to the external one. That's why we call them autonomous system boundary router, not area border router. Area border routers belong to the same OSPF domain, while a SBAR belong to OSPF domain and alway and also different protocol. So it's like a gateway to external network. It's due the redistribution from different protocols, static route, EEG, ERP, BGP, and rip in other. And also the summarization are done an SPR and this is a router which connects us to do different protocol. Let's go back to our topology. So I just connect a cloud here, by the way, just to show you, there is nothing basically just a dummy Cloud Connect so that I can show you these are the external network. Here we have one cell to 216-17-0230. Here I will create a loopback interface is here in R1 to show you. And we will redistribute. So it will make them like external for us. So R1 play, roll up a SBAR because it's connect us to different protocol. Maybe here is EIRP, sorry. Maybe it is EI GRP, maybe here is BGP, maybe here is, IS-IS. It can be steady anything. So this router play a role up a SPR which connect us to different routing protocol. I hope so you get the idea of four different role. Now coming to our topology, how we can find out in the lab date which router play which role. The first one, I will make R1 as an SBIR. To make them SBAR, I need to connect them to different protocol. So the easy way is there is a loopback interface. If you remember. You remember show IP interface loop back. Here is a loopback interface. And what we done, we advertise this Lubeck and the OSPF show running section, OSPF. So why not just remove this one and we will make them as the external. Here is basically is belonged to areas zero. So what I can do, I will go to configuration router, OSPF one, so that we can do a test. So I will say No, you are not belong to areas zero. So let me remove them. And then I will say redistribute connected. This is the command because these two are already advertised, which is here. So which one is the connected interface tests the only interface because I removed them. So what they, what they will do, they will make them as redistribute. They will redistribute this. And R1 will play the role up. Asb are done. So this is the only thing to change the environment so that I can show you all the four different type of OSPF. Now coming to verify how we can verify we held to different command show IP protocol and chew IP OSPF. These are the two commodity which we can verify what is the role of the router. So let's go to our topology and let's start from R1. So how we can find out, so type show IP protocol. And if I type show IP protocol. So here it's written that it is an autonomous system boundary router. And that's what I see. They said this router is a SBAR autonomous system boundary router. Okay, because we redistribute. Redistribute means we are connected to external network and the lab you can do such way. We verify from here, this is the first command. Second command show IP OSPF. And when you type this one, and let's go down somewhere, you will find the same things which we just saw. So let me go down, let's see where it is mentioned. And let's go up. Here is they mentioned that it is autonomous system boundary router. The router play a role up autonomous system boundary router. So this is the second command to verify. We will come to area border, Saudi big bone, area. Forget about this one. Again, the same command we can use, but right now I just want to show you the SPR, autonomous system boundary router. Now let's go we discuss area border router. So in our topology, or R2 and R3 play rollup a, BR. Let's verify. Let's go to our two. Similarly in R2, what we can do type command show IP OSPF. And when you go down, so it's written here. It is area border router, not like R1 mentioned. It is autonomous system boundary router. R2 is, it is area border routers. And similarly, R3 is also the same. So if I type a command show IP OSPF. So here it is, area border router. And also you can verify by show IP protocol command is well, if I type show IP protocol command. So the same thing as written here. It is area border router. To router play a role up area border router because it's connect different area and our topology and it's true. Now let's go back to verify backbone router. So what we say about big monitor, I told you that any router which is partially connect two areas zero. Keep the word partially connected to areas zero. We'll call them a backbone router. Let's go to our topology. Here. I can see only one partially belong to interfaces, belonged to areas zero, r2, two interfaces belong to areas zero in R3 to interface belonged to areas zero. So I can say that R1, R2, and R3 are called Backbone router. Let's verify the same command can be used, which we previously used. And there it is. Sure IPO SPF, if I go down. Here is a threatened that area, backbone zero, that this router belongs to big bone area. And similarly or two because two interfaces belong. So if I click here and see here is area backbone two. Now let's go back to R1 and R1. Similarly essay area backbone. However, if I go to R4, it will not be there. If you are thinking maybe it's written everywhere. No. If I go to R4 and type the same command, show IP voice PF, and go down by space bar. So it is not mentioned here that this is a big bone. It's mentioned area of one, which we call them areas of the backbone means any other area. You get the point. Yeah. So this was a backbone router. We verify that any router which partially connect two areas zero, the one interface or more interface fall in areas zeros. So there's router is called backbone router. But I told you one thing more, that router can play more than one role, such as the example of media time or further, but I am a son of someone as well. So in this case, R2 and R3 player to roll. When R1 is well, one is HBR as well, and big boned area router as well. Or to a BR is an area of big bonus and ABR as well. N is belong to oh, big bone area is well, I hope so it's clear. And finally we have internal router. So any router which belong to the same area, all the interfaces, not a single interface to any other area. So they wrote a race car, what is called dead area is called internal router. And how we can find if a router is not embed bone area and if R outer is an art ABR, and if a router is not a SPR data router is means that it is internal router. So in our case, R4 and R5 are the only router which belong to a different area and they don't play any other things. So yes, it's belong to area of one and all the interfaces are in area one. And similarly R5 as well. So if I type show IP OSPF, and it's better to type section area. So it's area too. So that's why it means these two are the internal router, the tip, I hope so It's clear that these are the different OSPF router type. Okay. 11. OSPF Different Routes Types: Next topic related to OSPF is the routes type. Previous one we discussed routers. Router play different roles in OSPF domain. But this one is different routes, the routes which coming to the OSPF routers routing table. So always be a Froude, come in variety of shape and size and distinguish between different types of routes and routing table. You will see different type of routes in the routing table of OSPF. Typically represent n 0, 0 means OSPF. However, you will see many other type as well. If you saw like this 0 and there is a star and I add means a default route. And if you say only, so it means this is called Intro area route. Enter area route, originate, and learn in the same area. The route which is learn in the same area. Those routes are called intra area roads and they are marked with 0 because they belong to the same area. They are coming from the same area. These routes, what does it mean? N dry area Route, same area. So R1, R2, and R3 belong to areas zero. So these route, which is coming like a 10,113.10, 23. So these will be mentioned and R2 as entrance area. Let's go to our tool to see if I type in a command. Show IP route, OSPF. I say Show me Hulu SPF routes. Here I can see different thing. Always deer or will be there. But with all there can be many thing such as 0 means OSPF. But there is inter area as well. And there is external type. One is external type to Israel. And there is external type, this one as well. And it should be many other more as well. Here the one which I'm interested right now, which we are discussing is intra area route, which is marked with 0. So the one which is marked with all these, they are coming from the same area. So the route which is coming from the same area, I'm going to give you an example of this one. Take this example. I'm an R2 and sorry this one, only this one. So ten dot one dot 1310 dot one dot 13 is this one which belong to R1 interface. So when R two is receiving ten dot one dot 13, so they mark them with 0. And they said this is intra area route. This is called Intro area. They said that they are coming from the same area, the area which I am belong to areas zero. So this route also belong to area zero. So this is why we will call them entrance area rho, I hope so It's clear. Now going to enter area, the route which is entering this area, which do not belong to the same area. The route which is coming from another area to this routing table, we call them enter area. So you can memorize like the route which is inter in this area. You will recognize them by the rays enter. And it will be marked with all the route which is coming from different area. So if I go to R2, R2 receiving area one routes. So it means this route will be mark with 0. So let's go there. And here is here is the route which is coming from different areas, 172 to 30 days. One is coming from R2 to R2. So they mark them enter area, we call them enter area with 0. N here is 0. You get the idea because these routes are coming from different area. The area which are two is not connected. So get the idea R2 is coming here, so they call them enter area. Now, another type is external route. External route. The route switch is coming from external protocol. Represent with different thing. We will discuss this later in the course. E1, E2, it can be N1 and N2 and many other. Anyway, any route which we represent by either e to either N1, N2, these drought are coming from external route, external means, maybe from any other protocol or maybe redistribute. So how we can notice one, like this one and R1 I redistribute for, for external. R2 will resume for, for E1 or E2. Let's see. Here is E2. You can see there's a 444 is coming from external routing protocol. Somebody gives me this one. A is b are given me a SBRT say that I take this routing from static, maybe from EEG, ERP, maybe from BGP, maybe from any other protocol, IS-IS. And let me give you either it redistribute and let me give you, so it will be marked with 0 e to, I'm not saying E is dependent. It can be N1 as well, it can be N2 as well. There are different scenario. We are not interested in that right now, but anyway, we are getting this with E2. So now we know why this is the air. Sorry, this 0 and y 0 is there. So now we know this one, and now we know why. Oh, E2. And we verify this one. And also we verify the other one as well. And this one, these are the different routes with coming to OSPF routing table. I also this one when you make a default route. So it will show you this one. I did not show you this one, but anyway, I show you enter the area the same area out with oh, I show you the entire area route which is coming from another area with all the external route which coming from external protocol with E1 and E2. I hope so you get the idea. See these are the different OSPF routes type, which coming in the routing table. And what does it mean every mark? So now you know this one. 12. OSPF DR and BDR Election: Next topic related to OSPF, SDR and B DR. DR. Means designated router and BD armies backup designated router. Dr is like a team leader and a B DR is a backup team leader. There is a manager, there is many other roles, but one of them is the team leader. If you are working in any organization, you need a team leaders so they can manage the things properly if you have any issues. So they will discuss with the top management. Similarly, because you are working 20.30 people and organization is employee. And if you have an issue and if you go directly all abuse 30.40, 40 employees to the manager. So it will make a broadcast. How you will explain them, each and everything. Everybody, we start that yes, I have this issue. The other we'll say this is my issue. So we need a solution. And the solution is rather than all these 20 employees go to the manager to discuss the things. Weiner, we have a team leader. We will give out everything to them and he will go to discuss. And this is how the things working in an organization. Similarly, OSPF, if they have a broadcast network. So what they do and broadcast network, they choose DR and BTL. They do election. And based on that election, they select DR. designated router and backup designated router. Dr. Is the router which are the distribute updates on the same segment. Because the reason is if you have a broadcast network, so everybody will start to communicate with each other because we told you that if there is any updates, they will send a multicast packet to each other. Some same like this one. Suppose y1, this is for router. And suppose they want to send an update this router. They will send up that here as well. They will send because they belong to the same broadcast domain. The router are connected to one same broadcast and they will send the packet here as well. Now they will have to reply, they will have to reply, and they will also reply n. Similarly, if they have some updates, so they will send update here, they will send update here, and they will send update here. They will reply to the ear and they will reply and this one will be reply. Similarly, if something goes wrong, something change. So again, the same process will be done. So you see, it's like a broadcast from everybody start to say hello to each other. Everybody has dared to, they will start to send eat because they all are connected to the same broadcast domain through switch. Suppose I make them more registry that you can understand. And it is a big issue. Same example I gave you when you go to your manager to discuss and you are, if you are more than 20.30 employees to discuss the same thing or different thing. It is a big issue. So in this case we SPF what they do and such domain and such broadcast domain they say, Okay, it is a big issue. Why not let select one person as a DR? So suppose there select DR. we will discuss how they select here. Suppose R1 is a DR. Now let's go back to the same scenario. If this router has some update, they will not send them to hear. No, they will not send them to hear. No. They will only send to this is a beer. They will send them to DIA that there is something which has changed. I want to say, okay, let me send update here and send update here. That's it. Now everybody know. Similarly, if this router has something they will not send to all, they will send them to R1 and R1 will update these. Now in case if this rotor is down, for some reason, the team leader is not available. Maybe he on vacation or something. So we need to choose another router when this one is not available. We call them BD. So this is the scenario, this y and OSPF, they choose a DR and BD. So DRS D, responsible to end the same segment to send and receive the update and update other router and the same domain. Keep in mind. It means there are three terminologies. The router, which is the King, we call them DR. And the other one is BGR, which is the second option is a backup and all other router or D, or other three things. End the broadcast domain. We have our dear, we have our PDR, and rest of our routers are called D or others. Okay, these three things are clear. Now, coming to how they elect a DR and DR by default. And then we can elect any router year so we can change the priority by i2 is a priority to choose any router as a DR. And our choice of prouder we can make them or DR. Buyer define the priority is one. And if you make the priority zero, it means they're doing want to participate and DR. And build election. It means they're don't want to give to anyone. Maybe there's a no, I do I don't like anybody. I don't want to give my word to anybody. If you make the priority zero before this one, Let's see, it's one or not. Okay, It's not configured. I maybe. So let me go to R1 first. It may open that waste PFS configure or not first we need to see this one. So nothing is configured here. So let me open R1 and let's open R2 is well, okay. Let's open our three as well. Nothing is configured. I will copy paste because we know how to configure OSPF. And let me know this one. Let's start. Now we know that by default the priority is one. And if you make the priority zero, so it will not elect DR and VTR. Now coming to DRP, DR. election, how they elect DR and BD. So by default, the priority is one. So it means every router, the priority is same. They're different. Priority is one. Now how they will choose if everybody has priority one. So the router, which is configured with highest priority win the election. But every router has the same priority. I told you if you make the priority zero, then it will not participate in election of DRP TR. This point is also clear. Now, if the router priority is same. So the tiebreaker is how years router ID the router with the highest routed idea and it's not possible the same router, IT and the domain. Because I told you last time, I think so last week we done, if you give the same router ID in the same domain, is like a one-two-three brother has the same name is not possible. Every router has a different router. It and what is router ID we discussed last time in detail. I don't want to go in. The router with the highest router ID is a tiebreaker, and they will become the DR. And then with the second highest priority will become BGR and all other router will become d or other. So now this point is clear. But keep in mind. Suppose if a router has the highest priority, but it's come alive after the election. So no, it doesn't mean that if the here's our highest priority, either highest router ID and it started the letter after the election. So it will never become their DR. Suppose an organization 20 employees are working and you or the team leader. But a new person came, which has highest education and highest certification and high experience. And he joined on the first day and he said No because my experiences more than this guy, let me, I will become the team leader. Everybody will say No, this is your first day. You don't know anything about this organization and this guy is working since 23 years, so he has a team leader. You need to stay here. If you leave the team leadership, then you can become, first you need to know about the network. So it's not possible. Similarly, the router with highest priority but in the time of election if it is not available, so router will never become a D or F, it is a line after the election. Similarly, I give an example in real world. That's why I mentioned it will not become our DR. Neither video until the IRB DR. routes fail, router fail. If any of these fail. So the process will start again. Their DR is not available BD or is not available. Let's do the election again. So in the new election, then that router can become a new deal. You get my point. Second thing, let me mention. Suppose the election is done. One router become DR and other become BGR and router the DRS down and BD or become a DR. Now, the actual DR a line back. There is no preemption preemption rule which we've done. It doesn't mean that the DR come back to it will become DR. again, no. There is no concept of preemption supported and DRP. Drp. Same like HRP, VRP and GLB P, which we them It's not like date the router, which is what PDR because DR. was down, it becomes DR. When the actual DR. come no. It will be d or other it will never become the R&B DR. the routers or down. Are you statically reconfigure the process of OSPF? Now this DBDR do communication and this IP, the communication between the RBD or R2, 24006 and other halo multicasts and everything are two to 4005. We discussed on the first lecture up with these two. I told you that I will tell you about two to 4006. I hope so theoretically you get the idea. Now. Now I have this topology. We will configure out 11,922.60 at one, this is two, this is three and this is four. And then we will configure OSPF and this router. And then we will see which router will become their DR, because we have a broadcast domain. R1 is configured are two basic configuration and then we have our same command to apply because I belong to the same network. And then we will verify with the help of shoe IPO SPF neighbor to see the DR and so the video and also d or other end priority which is the default one. And we will see why it's become a DR because of the highest router ID we will see. And then we will change the priority. If we want to make any router adhere to, we can change the priority anytime. From priority, the highest one will become the year. So let's see, let's go to our lab. We have four routers, R1, two, which is nothing is configured. So we're going to configure by script. Okay? So let's go to script. So we said just configured IP and disable a CDP because it will make an error or UDP because you are connected to switch. So it will give you the error. So that's why I just disabled and paste. And so R1 basic configuration is done. And R2 has also one interface to configure and change the name done. And finally, we have our three, only one interface to configure and change the name. And finally we have our four. So same thing, we're going to apply it to our forest. Well, now you know how to apply the script. Yeah, I hope so. And finally, let's configure OSPF. So we have the same command on our router. We don't need to do anything. We say router, OSPF, one network 16081, because all belong to one network and all of them has to advertise in the same area. So R1 paste this command, R2, same command. And R3 configure OSPF and R4 configure OSPF. And we're done now we need to verify to see. So now you know that each router will become BR and which will become the PDR. The time of election, all the routers are available because we just configure OSPF router are available for election. Now the first thing they will check the priority, priority of all router R1. Second thing, they're going to check the highest router ID because we never configured Lubeck. So all the router will take the interface IP. Interface IP is 1.1.1.3 and one dot for the highest router ID will become one dot for, I hope so, R4 will become dear and R3 will become BGR. Let's see. So now the OSPF is done, the process is done. And if I check here, show IP OSPF neighbor command. They said they'd one dot for is are d, one dot d is a BD, which we expect it will be. And if I copy the same command in R2, and let's see here. And if you go to R3 as well and paste the same command and R4 as well, which is our dear, by the way, because this rotor is DR, so it's not showing us the DR because this router is a DR. But it's best to find out in R1. So R1 say that the neighbor id, which has 192.60, 81 dot for the state, we discussed it yet fully stirred and two-way street, if you remember. They say R4 is our DR, and R3 is a BCR, and R2 is d or other. These are the three role which I told you. Even R1 is DR. Other we can find out from R2. R2 said that one, that one is also D or other. The router which you type this command, it will not show their own status. So now we have our DRM be DR, which we expect that the router ID, Let's see, R4 router IT, maybe you forgot that outright issue, IP OSPF. And here is the router. The router with the highest router ID will become a DR. Because this is a tiebreaker. Router priority is same, which is 111. We discussed this table by the way as well. So I don't want to go in detail. We discussed three different table. One of them was a neighbor table. So I'll router has the same priority debts, why they do this one? Okay, so what do you do next before to change this one? Let's go back to this theory I show you and I to do something. I told you that preemption is not supported. Reach router is a DR R4 less down the router router for what I need to do, Let's go to R4 and let me suspend this link. Either shut down the interface. It can be anything. I'm not saying to suspend excess cement is not available. Just shut down the interface is better to let me shut down. Maybe you are looking for the suspend link and it will not work. So let's go back to R1. And okay, it's still DR. this one. So we bring back this one anyway, it was done. So let's see. Let me down the interfaces. Better. Interface is useless zero and shut down. Now because R4 was a DR, which is down, it's not anymore. Now are three will become a deal. Now, everybody know they shared the communication. They say that our neighbor is down entered timer expired because the time is very important. It has to be, you remember I showed you this timer. Let's hear it for 40 s to they can flush this one. That our food is not available. Our team leader is on vacation. Let's make the backup person is a DR. So R three will become the DR. And let's see. Let me go back and show. You see it said that one dot three is our dear. One dot four is not anymore beer. But this is not my point. We know this one because he is a backup before it was a backup designated router. So definitely if DR is not available, they will become a DR. But i to do something else, let's bring them back. No shut down. And let's go back here to this point. I to looted and designated router and backup designated router. There is no preemption concept for DR. Fail BD I will take this has been done. However, when the router can bake designated router, it doesn't mean that it will become beer. Again, this is my point to show you. Our food is big and everything is done. Yeah, I believe Let's go back and see what they say. One dart for is d or other. He said one dot for is not anymore UNRWA media because the media rule has been given to one da2 when he was not available. And wonder three become a DR. So when wonderful, come back with the highest router ID, there's a no. You weren't the vacation now you are back. It doesn't mean you will become a DR again. Either. It can be if you run a command clear IP OSPF process. And you've done this one and all router. Then it will do the process again. And then they can become Yes. Dennis, possible. You get my point. And now let's check. After awhile when they become an I-bar. Let's see, because it will take time to become a neighbor. And then when I check this command, so then it's possible that one dot four becomes DR. And these are the start x start state. This is to waste it. Still they're processing going through their state which we discuss those two it by the way, let's see, uh, still two-way and the other is x star. And you remember in the extract state, they will choose a, DR and BD are a few. Remember I told you, now this is the day you can see that x starts there. They choose DRM video. And let's come see. It's almost done. But anyway, you can see one dot for is a DR. And after a while they will say one dot three is a video. Now I hope so It's done. Okay. Yeah. So now you can see one dot for is their DR, and one dot three is a video. This one is clear to you that if R outer is a DR and effort is down and come back, it will never become a deer until you clear the process either. All the things up OSPF is reconfigured again. What other point I told you that a point I told you that if a router with the highest priority command line after the election take place, still it will not become the DR. So now wondered for a has the highest router ID and we expect this, it will become a deal. What happened if this R4 is down? Okay? Interface easier to slay zero even let me say that. Let me configure this router. Stop. By the way, let me clear all the process. Either it will make the other router, Let's see, wondered for us to let them down, okay, because it will take 40 s, two down, one dot for 21, 26, 23, 22. So they can wash out and they can choose other DR, one dot three will become dear. Okay. And it's 12 second, 11 s until the time let me start this router as a fresh router with highest priority, highest router ID, but nothing is configured. It will start now. So let me start a new router until, let's see what happened here. Because only these three router are available. So they choose one dot three is a DR and wonder too is a BT or it's okay, which we expect this one. Anyway. Here is a new router which is started just now out of four. It's not yet started. Nothing is configured here. I will configure how use priority as well. Even though it has the highest router ideas. Well, do you think later on the selection is done? Or three, become a DR or to become obese and R1 become dear other. Everything is done. Now. R4 started just now as a new router. And here it is. Nothing is configured in this photo. Let me copy paste the command of R4 again. Okay? And it's a freshwater recently here. And let me configure with PFAS. Well, here it is. And also interface, interface easier to slay zero IP always be a priority is 200. So the priority is high. The router idea is high. But the only thing he just joined the organization with the highest education, with the highest experience, with the highest everything. And he said no because I have high yes. Education and I have more experience. Make me a team leader. This is my first day and make me our team leader on the first day. Do you think is possible? No. So similarly, OSPF say no. Let's go back and see forest come with the highest priority, two-hundred. And the role is D are other. But we say that the router will become a DR if they have the highest priority. Other three router priority is one and y, one dot for priority is 200. Yes, we said this, but at the same time, not if a router has high priority and come a line after the election. So I'll show you it's come after the election. So no, it's not possible. Yes, it is possible if we clear the process and do the things again, the election again. So clear IP OSPF process enter and yes. And if all the libraries down and next time when they're on, they will say, okay, this guy has highest priority. He win the election and let's make one dot for as a DR then as possible. However, come on line later on after the election. I assure you it's not possible. I hope so these points are clear to you why we are using the VTR. What is in the broadcast domain? They will make a broadcast strong. That's why they need to elect one person is a deer, another is a video. And then we verify from here. And also under the interface you can always make the priority high to make any router as a DR, It's up to you. However, you need to apply clear IPSP a process to apply this method. So that's it to shut down. I show you this one as well. So let's go back and this term, Let's see. Sorry, I type ps, which is wrong. So let's go back to R2 and verify here, show IP OSPF neighbor. Okay? And okay, because I did not clear here the process clear IPO is peer process. You need to do this one in our router, not in one router. So clear IPSP of process. Clear IPO is P of process. And also clear IPO SPF process. And I believe I already done here, yes. And I believe you I already done here as well. And now, after a while when they become an I-bar, so definitely are four will be the deer. Let's go back and show IPSP of neighbor. They are in two-way process. After a while, all the router are still MDR other. And after a while they will do the communication with each other. They will do the election. And finally they will choose one dot for is a DR. Okay. And maybe they select No, Not yet. 1234, they become night, but just now because they're taking time, we all know this routers is a bit slow. Here. It's now come up. It's okay. Now, let me do so DRP, DR. both are selected now. Okay. It doesn't mean the router with highest router ID will become a deer. A router with the highest priority is the first thing. Though you can make any rotor of these two baker DR. suppose this one is the lowest router idea, just go to this interface. And under interface type IPSP, a priority, clear the process and this router will become a deer like R4, which I show you. So I don't want to waste your time. You already know and now you know what is DRP, DR, and how to make any router D RBD. And what is the condition? I show you the condition as well. 13. OSPF Equal Load Balancing: Our next topic related to OSPF is load balancing. We discussed load balancing and detail, if you remember, and EEG ERP. However, I told you that an ERP, we have equal and unequal load balancing and we done in the lab as well. But this is not in the case of OSPF. Ospf only do equal cost load balancing. There is no concept on unequal load balancing. You get the idea because in EA GRP, I told you that EI GRP has the only protocol which support equal and unequal load balancing. And I hope you know the difference between equal and unequal load balancing. Similarly, OSPF also do only equal cost load balancing, which we call them ECMP. And we've done a complete labor and ECMP as well. And static route, if you remember. Ecmp has basically, if we best route to the destination, multiple best route, all routing protocol has a concept to install the same route and the routing table. Because metric is same protocols, same administrative distance is same. Everything is same. We discussing ECMP, if you remember, they will install those route and the routing table because best route go to the routing table. We have a multiple part with the same ID, multiple paths with the same metric, multiple paths with the same protocol. So finally, everything is same, same cost, same everything. So what they will do, they will say, okay, let me insert and let me install the same route in the routing table. And we will do load balancing, some perfectly dissent on one part and some traffic will be sent and other path. Okay, this is the same concept and I'll protocol and we discuss in detail as well. So similarly, OSPF do the same thing. By default. I believe it's installed for maximum. However, you can increase them to maximum 32 path. By default, the EHR period was also four, I believe I remember and I show you let me see if I go to that one. So maximum path, you can use maximum path command. You can increase if you want. So if I go to R to show IP protocol, and let's see how many partners support by default. So maximum path is for, but however you can increase them. So by default it will install for equal, there is no consequent n equals to live it. They will install equal cost part and the routing table maximum for what will be the criteria if it is more than four, the first-come first-serve basis, they will install doors and the routing table either you need to increase with the maximum path command under OSPF. So this is called equal cost. Now, we held the same lab which we configure previously. We have areas 01.2 are to basically receiving ten dot one dot 13 with two different way, you know, with this way, with the help of R3 and also R1. And there is one interface and dear S1 interface. So the cost is same here and the cursor same here with PFAS configured here, with PFAS configured here. Metric is same here, metric is same here. Same here, cost is same year, destination is same, destination is same. So what they will do, R2 will install to equal cost here, to reach to ten dot one dot 13. So this is the same way. And we need to verify from here, we have two part to reach to tender 13 and also from this way. So we don't need to configure anything. All the thing we already configured, OSPF configuration is done. You already know we just need to verify these things are already done. Nothing needs to be configured. And let's verify an R2 with the help of show IP route OSPF command. So let me go to our topology and let me open out two. So if I go to R2 and type here show I'd be OSPF, route, sorry, show IP route OSPF. And if I type a command and see they're telling me I want to reach to ten dot one dot 13. And here is they say that if you want to go to ten dot one dot 13. So there are two ways. 11, same administrative distances, same AWS SAM, causes same cost is, and we know how the cost is coming. I hope so now you know why is written to this is coming to R3 and this one is coming to with the help of R1. And we already discussed these as well. So you see load balancing, how I know load balancing. So we can verify it by another command. This route, and I said ten dot zero dot three dot is 13, I believe. 13, That one. This 110.1.1.1. I said I want to go to ten dot one, dot dot one. And let's see what they will do. A trace route and dot zero. It's not zero. I believe it's one year or ten dot one dot 13, sorry. So Control C, Control Shift F6 to create this one and just make this 11. And also let me type numeric so it will quickly, you see is going through way that 1.23 to two, this one and that one dot, dot 1.10 dot one dot three dot t2. You see two-way. Lets me do again. Again. I say 23 dot to that one. Again, Let's do that. 123 dot two. They say I can reach to this, so it's doing equal cost. So let me show you buy another way. Show IP route. And what is the command? Ten dot one, dot 13 dot one. It was 13. That one, Yeah. Yes. So here it is. I say show me the entry for this route. If I want to reach there, they say, okay, we have two different paths to reach the administrator to distances 1110, metric is two, and this is the interface to go out. But however, we have another one, perfect sharing count one and traffic sharing count one. So we have two interfaces, G zero slope zero and G zero slash two. Yes, zero slope 0.0 slash two. They are doing perfect sharing count one. I showed you this command and GRP is an equal cost. There is no consultant and equal, but this route is by default here. If we have more than one. So up to poor will be installed, which I show you that if you can type show IP protocol. So after for up to four, sorry. You can install them and you can increase this one if you want. By default as dear, I don't need to do anything. So if I go back, show IP route, show IP route OSPF and Enter. By the way, let me make them more specific section. And this is a roll so that you can only see this one. Here is, let me increase and here they say, I will do equal cost. This one is the next top, and this one is the next talk. I also is clear. We saw this one and we verify. We verify it by show IP route command and traffic shaping current one and also by trace route command is going through same way, too different way. Similarly, digit, so this was the equal cost, load balancing and OSPF. They are due by default. We do need to do anything. There is no concept of unequal. So that I can show you, which was in DEI GRP that said this was the USP of load balancing. 14. OSPF Summarization Theory: The next topic related to OSPF, OSPF summarization. By the way, we done summarization and EEG ERP. So you already know theoretically that what is summarization? Suppose if you have a multiple route and you advertise them as a single route. This is called summarization process of summarization subnet and two large subnet to advertise them. You know, as a one subnet to your neighbor is called summarization. It means a feature which is allow routing protocol to summarize the route to their class full network because we will make them as a class full network. The only difference between summarization and EEG, ERP and OSPF. Ospf you can do the summarization and two places only. So summarization is not possible in any area. It's not possible. It's not EA, GRP or rib to do summarization anywhere. We know route summarization help to reduce OSPF traffic and consumption. So OSPF, unlike year GRP, doesn't support automatic summarization and route aggregation. There is no concept of automatic summarization as well. If you remember any AGRP, we've done two type of summarization, automatic and men, while I show you both here, there's no concept of auto summarization because we can now do summarization every year, a new SPF network. It's also not possible. The only two places where we can do summarization is ABR. You remember I told you that in ABR and area border routers, these two are the router which are responsible for summarization. So you can only apply summarization and area border router and do number system boundary router. Not every beer. And also there is no automatic summarization like EA, GRP or rip. It means that summarize route from one particular area into another OSPF area can be done and ABR and the summarization can be done in ASP or if you want to summarize the outside injected route and OSPF is a summarize either wise versa. So these two are the router which played the role of ABR and SBIR. You can apply summarization here only. This way summarization is we discuss any AGRP as well. It will save route CPU, router CPU and RAM resources. So summarization can be used route manipulation by using Longest Prefix concept to reduce the routing overhead we are using summarization. If we have a huge routing table, we can summarize them to send them as a one, a two, and this way, there will be no burden on CPU. So what is the advantages which we discuss, any AGRP as well, save memory, bandwidth, same CPU cycle and stability as well. I show you stability as well and the AGRP, if you have many loop back interfaces and use summarize them. Until all the Lubeck is not down. It will not flip the network. But if you are advertising separately, so any interface which you down debt will be flipped. This is the advantages for main advantages of summarization is save memory, save bandwidth, savings, CPU and stability is there. So now we know the summarization, which we discussed by the way there as well. So as I tool use summarization can be apply an ABR and it is beer because area border routers connect different area. So if you want to summarize their traffic which coming from one area and you want to give to him the other area as a summarize. So yes, you need to go to ABR to do the summarization are if you held differently external connected routes and you want to give them OSPF domain and you want to summarize them. Again, you need to go to a SPR. These are the only places where you apply summarization. Restaurant any other places? Also R2 summarization is not possible. So now we know OSPF summarization. And what is the difference between an EA GRP summarization and OSPF summarization. So in next video we will configure summarization because in our topology, these Lubeck are coming from this one to ABR and also these Lubeck are coming to this one. So why not to do the same thing which we done in ERP to summarize them, but we're not in R4 is not EEG ERP and not in R5. Summarization can be only done in R2, which is ABR. Here are three, which is ABR, and if these routes are coming from externally, so then we can configure summarization in a beer. But there is a different command for ABR and for SPR. To summarize their trophic, we will see that one as well in the next video. 15. OSPF Summarization LAB: So in previous video we discussed with OSPF summarization. Now let's do OSPF summarization lab. We have this topology which we are using since in EEG ERP we held the same topology. Here we have our 12 or 55 different routers. R1, R2, and R3 are connected in OSPF, areas zero and R4 connected to area one in this one, area to this R2 connected to area when Israel in areas zero. Similarly, R3 and R4 we held different Lubeck and desert and R5 we have different loop back interfaces. This is our router image and we have a client, VPCs, ISPF, and process ideas. One, R1 basic configuration is done, are two basic configuration has done already. Similarly R4 and R5 basic configuration are already done. Okay, PC1 and PC2 configuration has done E101, OSPF configuration has previously done R2, R3, R4, and R5, and we verify as well. But before going to summarize, let's go to R1 and check the routing table of R1, what they are receiving R1. So if I go to R1 and if I type a command show IP route, OSPF will receive a huge number up network, which is this one. They're safe from another area. I am receiving these route a two different road and also these different a trout, which is these loop back interfaces from R4 through the hip hop R2. R1 is receiving a trout here and a trout here. This Why or why not is a huge routing table. Consider this eight is 80 or maybe 800 routes. So it will make a burden on R1 to search all the route and routing table. If somebody is going to any destination, they need to go through all the process to check the routing table. Now can I summarize these things? So R1 can receive only minimum routes, which we then an EEG ERP as well. Yes, we can, but we're an ERP. We configure summarization and R4 and R5, which is not possible. And OSPF we discuss theoretically, we need to go to area border router, the person who is on the border. We will tell them that whenever the route is coming from here, please summarize them. Don't send perfect to me. And this way we will tell to R3, which is a border router, which working on the border is army officer. We will tell them they don't allow all the route I don't need. Y is a huge burden on me. So R three will say, okay, let me do a summarization. And I will not allowed all the traffic to come to you as R1. Great. So what we need to do, we need to configure summarization and r2 for these road. And summarization and R3 for these road. Not an R4 and R5 is not possible. So let's go to R2. Okay? And R2, Let's go to configuration and a router, OSPF, one, which is our process. And what we will do. Now here the command is area. Summarization is done like this way. From which area these routes are coming. Let's go back to is receiving these route, which I want to summarize from area one. So let me type area one. And after that, the command is the range. It's a strange command. And after that, I need to type these summarized route, which we have done last time. By the way, you can use a calculator as well. You remember we've done this one. Slug. If you remember, I shared this route as well. Somebody wrote command. Yeah, there's somebody that old calculator I share with you. One thing When two to 16. Zero dot one. Okay. And let me copy and paste a time this 12345678. And let me change this digits, is sorry. This digit is one, this is two, this is three, this is four, this is five, this is six. This is say, well, okay, we have another one as well. And this is eight. And I say calculate because you done last time when I show you by bit by bit. So I don't want to do it again. So this is my summary route. And let me type here. And what is the subnet mask? This one. So this subnet mask, let me copy this one here. That's it. Done. So NR Do I say the route which is coming from area one and the range of 170 to 16 make them summarize and give it to firewall to R1. Now they will do summarization. So before this one, summarization, then for this one, not for this one. So now let's see again, if I show IP route OSPF this time, the first one will be summarize. Yes, so they make them summarize. You'll see it's not chewing on before it was showing all the route. No, it's not. And similarly, the same command, let me copy, but there is a slight changes. So let's go to our three and R3, I will say router, OSPF one. And let me paste the command, but I need to change two things. First, the area, the route each coming S2, and the 16 is 30. By the way. Rest of the thing is same. Here is given instruction to our three if these routers are coming from area to, please summarize them and give it to R1, R3, say Okay, and enter. So now let's go back to R1. So R1 is receiving 38 separate interfaces here. Now let's check out if everything is okay. So the routing table will minimize n here is not anymore. 170 to 16 with 217230 with 20. Now it's been summarize. It was so easy because summarization can not be done in any router besides ABR and a SPR. So R2 and R3 player roll up ABR. We configure area border routers, summarization tier. Okay, So this one is done. So R1 was receiving huge traffic, then reconfigure out to an area one summarization and area three or two summarization. And after that when we check R1, so it's become a small table, which is the advantages of summarization. Also you can verify an R2. There will be another interface. I already mentioned you the null interface. Why is tear and R2? Because you then the summarization dear, they will assign to the null interface if any, IP, which is covered last time somebody asked me and then I show you. So it will be destroyed by analogy row. So it will be there in R2. Definitely we know this one. Okay? Maybe you are thinking that the traffic will not go. Everything will work. From PC1. I try to ping all these, it will work. It doesn't mean that summarization means that nothing will work. So if I type 300 dot one, so it's working one dot one, it's working. That one, the opposite side is working. And three dot one is working. And similarly the last one is eight dot one. It will work. I'm pinging from PC1 to these, so it's working. It doesn't mean that it will stop working. Okay. This one opposite the other side is way, it will work. Now coming to the second summarization, which we configured in a SBIR. Now, because we will make R1 is the ASB or first. And also we will configure some loop back interfaces to make them as external. Then we will redistribute them. The first thing I need to go to R1 to make them as HBR, even though as a SBAR before as well. If we check show IP protocol, but only SBA, SBIR, only one loop back interfaces are there. Show IP show IP interface brief. But I want more to create and redistribute is already here. So what I will do router, okay, first let's create some loop back interfaces. So let me copy the command is easy to create here. So here is an R1. I will create nine loop back interfaces. So let me copy this one. And let's create the ***. And now if I checked blue show IP interface brief. So now I have many loopback interface is similar like other two router, 17028. That was once you'll do 216, This is 30, I make 0-868. This one is one, so two to eight. So I created yeah. Okay. This one is wrong, is 16, I make them. Maybe I done a mistake here because I copy this command from the other one. 172 to eight. So let me go to Interface Lubeck nine. And here type the command. This one rather than the other one is. And now, if I check here again, let's see us correct now. So yes, it's correct this time. So eight.01, 234. Okay, And finally, if you type this command, it will redistribute. By the way, this command is already there. No need. Okay, so let me copy and redistribute means it will consider them as external. I told you already, show running section OSPF. The interfaces we do advertising OSPF doors will be considered OSPF and if you type the command, okay, so redistribute is not there. So ten dot one dot 12.10 dot one dot 13 advertised, but not the other interfaces. So if I type a command, a router, OSPF one, and redistribute connected. So how many I have well-connected interfaces, those will be considered as a external blue show IP interface brief. From these Lubeck to tell the eight. All these will be redistribute. It means it's like a external network in the lab. You can do this one. That's why I mentioned here. It can be either GRP, it can be anything done. Now let's go to R2. R2 will receive all these route as an external. Hello. Let's check out, show IP route OSPF. They will say that I'm receiving e2. E2. E2. Here is a.one.234 5678. They said, I'm receiving these route from R1 as an external. R1, taking this route from external protocol may be connected, maybe static, maybe EEG, ERP may be BGP, maybe IS-IS. I don't know. And he gave it to me, is a huge network. Now, if I want to minimize, before I minimize an ABR, this time I want to minimize the route which is coming from external is a huge. So the procedure is different. Maybe I mentioned here, this part is done. We already done. Here is now the command is different. You see what was the commodity and R2 and R3 which we type it was arrange command. So if you do a summarization and ABR, the command is area to range and summarization. But if you want to do summarization and HBR, so the command is summary address, and it will summarize the external route and we'll give it to the OSPF domain as a summary. So let's go to R1 and apply this command, and that's it. We are already in OSPF and type this command and we're done. And if you go to R2 previously, they were receiving all these routes separately. Now it will be summarize. So if I type the same command again, and now E2 is only 11722800. Previously it was, E2 was nine different. And now it's become. So these are the two different way to do the summarization. And ABRs are different and HBR is different. Also, we know that summarization can only be done in a beer and a SPR, and both are different. There is no auto summarization. These things you need to remember what is the difference between EEG ERP summarization and OSPF summarization. And we're to apply these summarization. That's it. 16. OSPF Filtering Theory: Next topic related to OSPF is filtering, either filter, filter and normal word we are using filter. It's called filter. You can see this picture. So it's like a filter. Similarly and Route filter, what we do, we basically exchange routing updates with each other, the routers. However, if you want to accept or deny any route, update, our routing updates. So you can use filtering to filter them that I don't need this route, don't send me. So you can configure filter so it will block either. It will be accepted, it's up to you. You want to create a filter to allow the traffic, either to deny the traffic. We are talking about the traffic related to routing updates. So far did purpose, you can use filtering. Suppose an R1, I'm receiving all these route. Maybe for some reason in R1, I don't want this route 192.68 to one because this router will send them and routing updates that there is a route. But if you don't want this. So you can apply filter and this interface and the routing you can apply the ACL are so many other methods and you can block these update. 192.60, 81 will never come to your routing table. So if I go to R1, show IP route OSPF. So through OSPF, I'm receiving 190 to 168 to one, it should be there if I go down. So here is 190 to 168 to one. This is just an example. You can block any route and you can allow any traffic related to routing updates. Yes, I'm receiving as R1, I'm receiving 192.60 to one network and my routing table through OSPF. However, what if I want to deny this update? So I can use filter? Now this filter, what they will do, they will manipulate the traffic flow and will reduce memory utilization and will improve the security. Maybe for security reasons you don't need that one. Not only this one but our Duke and block them not to send this route to R1. So it can be anywhere you can apply this filter. And R1 not to receive an R2, not to send them. You get my point what I'm saying. So you can apply it anywhere, this filter and this way you can improve the security. You can reduce the memory utilization rather than a huge table. You minimize them and you send them few route. Other, maybe they don't need this manipulation. We can use filter. Now there are many methods to use to filter this routes. One of them is access control list. Again, we're gonna do in this course and detailed access control list, ACL, we call them. We have another method, distribute list. We have a prefix list and route map. So many methods are available which we can use to filter the routing updates. Okay? The first one is ACL, Access Control List. We can use anywhere because ACL can be used for many purposes. Again, we're going to do this in detail later in the course, however, here just to tell you that you can use SEL for many purposes, one of them is to stop the route updates to allow year. We specifically want to use ACL for filtering purpose, not to block and allow the traffic, not to deny and permit the traffic. Basically, we are using fire to black and deny the routing updates. There is a difference between normal traffic and there is a difference between routing updates. You can use a CLP for many purposes. One of them is for routing updates, or we can say FIR filter purpose. However, later in the course we're gonna use HCl to permit and deny traffic, network traffic. I'm specifically saying you can use a seal for many purposes. There is a difference between routing updates and there is a difference between traffic. Okay, so this is the way to use ACL and OSPF far filter purpose. Second method is distributed list. This distributed less can also be used in any dynamic routing protocol. One of them is OSPF. To block the routing updates, either to allow the routing updates, the route which is coming into the router. Either they're always going out to the router. So you can apply for both. And distributed less is similar like an ACL to block the traffic, to block the routing update, either to deny the traffic to permit, are allowed the routing updates. It's almost similar like an ACL. But more specifically, we are using distributed less. And dynamic protocols such as OSPF to in-out are denying routing updates. And it can be applied an indirection, either an odd direction. What does it mean? Maybe I1 and I2 when the traffic is going out for 160 and block them. Or maybe when I'm receiving for four. So again, I say n when they're perfect for 44 is N black them. So you can use this distributed less far both purpose. Okay? Then the third method is prefix list. Prefix lists is also similar to ACL. Again, but it's more flexible than ACL. Again, you can use this prefix list to allow or deny routing updates. But in ACL, we only specify source, destination and source network or host or those things. But however, prefix list is more flexible. You can put a lot of thing greater than and less than. And so many other options that are available which is not available in ACL. So that's why you can use prefect list if you need more word style type of to allow or deny the routing updates so you can use prefix list. And the final one is route map, which I not mentioned because in BGP we will, next paper we will discuss in detail the route map. So you can use route map as well for filter purpose. So we have HCl, we have distributed list, we have prefix list, and we have a route map. All these can be used to filter any dynamic routing protocol updates when they're sending, are exchanging routing updates with each other. I'm talking about the routers. So these are theoretical part. Now in next video we're going to see how we can block any routing updates n, which is coming to our routing table so we can block doors and we will see. 17. OSPF Filtering ACL Lab: Let's start this time. We already discussed filter. So now let's do the lab OSPF router filter. We have the same topology, which we are doing all the OSPF stuff. So now we have the same topology, same everything we PCS we are using as a client and we have this router which we are using in this lab. We have OSPF already configured, R1 has configured out two or three, which we already know it's been configured. And now we need to go to R1. So these are the configuration which is already done. So the final thing is I just want to go to R1. You can block any, we're going to block a one. Either There's two which come into R1. So let's go to R1 routing table. Here. If I type show IP route OSPF. So at the end you're going to see 190 to 168. Here is 1.2. I'm receiving this from Enter area and it's here in case I don't want this one, maybe one or two. Don't want to receive the routing update for these two route. What I can do, I can configure filter. So let's go to config T and router OSPF one, which is our process ID. And first of all, I will configure ACL. You can configure name ACL. Either you can configure, sorry, let me go out first. Let me configure access list n, either name x is less, it's up to you. It's the same thing. So I want a standard ACL and just give them any names. Oppose black. And here I want to deny which trophic 192 6081 dot zero. And the wildcard is 000244. It means that check the first digits has to be 19, 2 s zero means second digit has to be one at 68, the third digit has to be one. And the last one. It can be anything, so it's 255. This is called wildcard. So simple. And then I say permit any because I want to permit rest of the trophic. Mysql has been configured. This is not for traffic blocking, this is for routing update because we're gonna do SEL and details. So you will understand we apply when we blocking traffic. So we apply ACL under the interface. But I'm not going to apply this ACL and at the interface because I don't want to block the traffic, basically, I want to block the routing updates. So it's done. Mysql is configured, show IP access list, and it's here, 10.20. We're gonna do this one. These are the sequence number and this is wildcard and it's configured. And now I need to go to OSPF router, OSPF one, which is process ID. And here I will use distributed list, which we just discussed. We have HCl and we have distributed lists. And we have prefix list. Route me. Here, what I will say, distributed list. And here it will ask me the ACL. Either it is asking the route map, either it's asking prefix. So you have three different method, whatever you want to use. So this time I use ACL, it's asking IP access list number. Either the name x is less than m. So if you have a CL by name so you can use it. And if you have HCl by numbers, so you can put number. And if you using prefix to the top, which I had done this one, it can be through prefixes as well. And it can be through route. Maybe it's up to you anyway this time you done through SEL so let me type the name and then question mark. I told you it can be filtered incoming routing updates, either filter outgoing route updates. So let's see the situation. So this is an R1. The traffic will come here. This 101, 68 to R2. R2 will forward it to me. So it means it's in here. I will say that traffic is n. So if I check again, show excess list, there should be denied yes and deny one matches here. And if I go back now show IP route OSPF or SPF. So there should be no more 192.60 81 network. Let's see. If I go then so too is available, but no more one just before there was one. Now it's not anymore. And if we check the ACL, as I showed you in the ACL, there is one match which has been blocked and 23 matches because the rest up a routing update has to be loud. So you need to type this command permit any that allowed rest of the routing of debt, but only black this one. So we use this ACL far routing updates to black, not for traffic blood. Because for traffic block, you need to go to Interface, any interface which is, and then here you need to type IP access group, which we will do exist group. And then you type the ACL Nam, suppose block. And then again in and out. This is for inbound packets, and this was when we type here, so it was for routing updates. So as I told you, ACL can be used for different purpose anyway, and here I use them for routing updates, okay, So there is a difference just to show you what else. That's it, I believe because we block them. So it was before here. And then I don't need to receive this route. Okay, so what I've done for that purpose, I create a ACL and then I use distributed less to call the ACL. And after the date this 10026081 network will be not anymore. Similarly, you can block any network. You can again use the same easier to block two as well. You can block any of these. It's up to you. I just give you an example of one network and you can apply other network as well. So this is called filter by the way, if you know this one. So the similar concept is an BGP as well. Router BGP, sorry, and EA, GRP, GRP, suppose one. So distributed list. Again the same thing. So if you know and OSPF is the same thing can be applied in EEG ERP, and the same thing can be applied in the repays well, and the same thing can be applied a bit change and BGP as well, because it's not including the outline and EEG ERP. So I just show you that in case if it is not include. So you can get idea from here and you can use the same concept and EEG ERP as well. Okay, So let me remove ERP. No router. Glp-1 because you SPF is running there. We don't want to be confused and that's it. So this was the route filter in OSPF. 18. OSPF Passive Interfaces: Another concept in OSPF is passive interface. Basically passive interfaces, data interface which not receiving any updates or OSPF. Suppose if you want to block wispy of update not to be sent on a specific interface or more than one interface. So you can make that interface basically we call them basically, same concept can be applied in EHR be same concept can be applied and rip in same concept can be applied in any other routing protocol if you understand one. So you can apply the same thing in other dynamic routing protocol because it's been removed any AGRP, but they include them in OSPF. So that's why we are doing here. Okay, So basically the interface. Now you may think why we need this one. So in two cases, I will give you an example. And two cases. One is this year, either in this case, R4 is sending USP of detail to PC1. Do you think PC1 need OSPF routing updates? Because we advertise 1902168 and OSPF. Let me show you our four. So if I go to R4 and if I say show running, and here I say section and OSPF. So because we need this one to advertise 10026081, so definitely this interface has to receive OSPF update as well. So let's see, here is 190 to 168. So because we advertise, so what will happen this For will send the halo packet up OSPF, this interface, and also on this interface. Here is the logic, okay? Because they need to make an I-bar ship with R2, but don't need to send OSPF year. Somebody here, a hacker or someone is here sitting. So they will, if they start a Wireshark, so they will get all the updates of the OSPF. And they will know about the network topology because as we know are four has to receive all the updates as well. So they will send the update. And this way is where even though there is no router. So what will happen? Suppose I, on a Wireshark, I will receive all the updates here as well. If somebody know the concept. So what they will do, they will underwater crooked. I'm receiving Hello packet because after 30 s. So if I go to SPF and I can see the whole network. So this is the header which we discussed. There is no authentication we know now. And the Hello packet, I can see 168 network and designated and backup designated detail. And I can open them and see more detail. And I can see the network detail. If I, if there is any updates, send, the update will be sent on this interface as well. And I will get all the detail here as I open them. As a client, I install a Wireshark. I'm receiving hello after every 32nd. So because this is the default behavior, one case. So in this case, if you have a local network connected, whereas no router anymore or switches connected. So you need to block OSPF not to be sent here. So somebody can get all the detail up your network. One case. Second, maybe if I hail such thing. Yeah, here like ISP. Suppose you have wispy of configured so many router inside and you euro is PFS configure your edge router, either be last router, which send the traffic outside to ISP. In similar case, like we are receiving OSPF. So definitely they will send a halo packet and this ISP interface as well. So if somebody on the internet and if they have a Wireshark or any other Capture tool. So they will get the entire topology detail here. Again, as a risky and it's not a good practice and not a security vulnerability. So what we can do if you are interfaces going out. So normally we default route configure. We don't want to configure SPF with the ISP directly. It's not possible. What we can do. We need to make the center first-person. And here in this case, we need to make this interface Basic. So in these two cases, you need to make passive interface. Just two cases. I told you use cases. Now anywhere with you don't need to send the Hello packet, block. Those interface make them passive. So this is called OSPF, basically interfaces. So now you get the idea. Now you have to come on. If you have more interfaces, such as here, they have three interfaces, only one has to be enabled. Ospf, you can type the command deform. It will make all the interfaces passive and then make this interface what is called active. Removed from the passive. Either you can make one-by-one interface spaceships, so it's up to you. And the interface which is become passive data interface will never make an eyeball shape and there will be no more hello packets. This for sure in this what we want, okay? So in our topology, what we will do, we want to block here not to be received on PC2, PC1. And our topology, we have this case and I told you the other cases as well. So what I need to do, I need to go to okay. Let me show you so I'm receiving yellow SPF. Let me type here by the way, how many I received or SPF. Almost how many packets, 39 packet I receive. After that it will be blocked. So let me go to R4 and R4 ICA, router, OSPF, one process ID. And here I will tip passive interface. Now, which interface is going to PC1, G zero slash zero. Okay. How many of two now 43. Okay. Now after that it will not be anymore. G zero plus zero plus zero here. Let me double-check. Yes. And now after 43, it will not receive any OSPF anymore. So let's wait for awhile because after 30 s they can assign hello. Yeah, It will never send anymore because they're too interface is now basically interface. They don't send neighbor and Hello packet on this one. So after 43 you will not receive. And how we can verify. So we can go to from here as well, show running config section OSPF. And it will show you the passive interface details here and here. So it should be up here. One place to verify. Second thing we can verify show IP OSPF interface, which interface G zero slope zero. So definitely because we make this interface passive, so it's here. They said, No, Hello passive interface. This interface is passive and there shouldn't be any more hello packets to be sent on this interface. So if you check any other interface, which is G zero slash one. So it's not mentioned here. They say hello, Do, and two-second. But here lets say no because we make this interface passive entropy. So this is the way to verify and similarly show IP OSPF, joy peace pipe night, but I believe a neighbor interfaces, so it has to show here. And if I type interface, I believe there is another command is well, if we hit g0g0 slash zero and there is no more, but if I turn G zero slash one, so there is an eyeball shape and this one, but there is no more anything on G zero slash zero because I removed the not to be saying hello on this side. Okay. They said this was the We're also you can make this way. So let me save the sitting and R4. So now this interface is not anymore to send Hello packets similarly, so we're, I apply this one in R4 and we have another one on this side and R5 pins with. So again, if you want to see, so if we captured the packet, okay, it's not showing. So let me start. So again here will be OSPF halo as well. So I need to go to R5 and I need to do the same thing. So let's see. First, you're gonna receive because I blocked on this side, okay, Not on this side. So let's go to Ethernet and lets us PF is there or not. So let's try with SPF. And after a while, because after 30 s here, so it's PFS coming and let's go to our fight and quickly plug this one. What is the interface? Same interface. So let's see config router, OSPF one. And before the third one, let's apply passive interface. G is usually zero and block them. So you will not receive any more packet because we just savvy to receive, but it's not anymore. For 30 s, it will send the halo packet we discussed. We're not receiving anymore. So this is the way let me save this setting as well. So now we apply the basic interfaces is well, let me close. We will be going to finance that 30-second, but it will never send. So we know for sure. I show you the command to verify. So let me close this one and now it's done. Let's go down what we have here. So I show you these interfaces where you can verify your algebra from the Wireshark, you can see them. It's not sending anymore. So this is basically the interface. Now keep in mind the same concept can be applied on EEG ERP as well. Router, Yager be one and passive interface, same concept, Control C. And let me remove this one. Exit and no router, EA GRP one. And similar concept when a rapist will rip and passive interface. Got the idea and no router. Let me remove them. So the same concept can be applied and repeat as well. And your GRP If you get the idea in OSPF, so it's similar, okay, they said, suppose if you need that, how we can do this one, N EA GRP either in red. So it's the same things. 19. OSPF Network Types Theory: Last topic related to OSPF, wispy of network type. First we need to discuss OSPF network type. Basically network define this network type. Basically how they will maker relationship, neighbor relationship with the other router. Basically OSPF, do different thing when the network change. Suppose if you have a broadcast network, so their relationship is different. And if you inhale point-to-point network, so the relationship, neighbor relationship become different. And real-world. Let me give an example. Some people you will see, maybe your friend or someone. They are very friendly even if they meet some new person. So they will become friendly with them very soon, very quickly. And a person like me, I'm shy, so when I go to a new place, so I cannot make friend quickly either in the job, when I change the job and go to the new place. So it's really hard for me to adjust. The ear is dependent on the person. Some person they are same everywhere. There, there not too much talking. Anyone if they go to any company anywhere in there with the close friends, they are the same. Hello, same behavior. So GRP RIP has the same behavior. If you configure them a broadcast network. If you configure them in non broadcast network, if you configure them and point to multipoint, point-to-point or whatever, they remain the same. The halo time are the same, datetime are the same. Agencies, the same routing protocol, rehabs similar in any network. However, OSPF, what they do when the network change, so they change the behavior and their behavior. We call them network type. They will see which type of network it is. Then they will react like date. Suppose you see some people when they go to some dancing place, so they will start dance. But if you send them to mosques today will become dead person. It's like a shape, like a water when you put them in a glass. So they will become a shape up the glass and when you put them in any other things so they will make dead shape. My main purpose is that first you need to understand what is the SPF network type. Because when we do the lab, so you gonna be confused, you will say What the **** is going on, why OSPF is changing and you're showing us these detail. The main reason is when you configure SPF and different networks, so they will react differently. And those reaction is basically five things. They will change the behavior of five things. And five thing is hello timer. They will change the halo timer. If the network change that timer, agency, it is automatic or manual. And finally, they've been seed to choose DR. DR. Know arias. Oh, by the way, for Devin change 14. So this is called network type, OSPF network type. Now there are five different OSPF network type. Cisco routers wanting to point broadcast, non broadcast point to multipoint, and non broadcasts point to multipoint. These are broadcast non broadcasts. Wine to multipoint, point to multipoint, non broadcast and point-to-point. These are the different type of connectivity of the routers. We're OSPF change their behavior. Those behavior is the halo timer. The dead-time on. The agencies will be automatically or manually and they will choose the RBD or no, we discussed last term, VRB. And agency means that you need they will find out the neighbor automatically is we know they will do automatically. But we're going to see some cases. You need to tell them that this is your neighbor. So this is manual procedure. And the RBD are you already know. And hello timer, interrupt timer I already show you and you know, after every time sequence we just saw as well. And passive interface after every ten second, by the way, there I told you 30 s, 10 s. After every 10 s, they can ascend a halo packet to check that the neighbor is available or not. They're going to wait for 42nd VSA. This was Israel. And after footie second, if the neighbor is not available, they will bring down the nine worship. And DLB. Dlb, I'll let you know DR. Is like a team leader and BD IRAC of the team leader is not available to be DRE is I give an example last time. So this is called network type. These are in this table. I show you all the thing and broadcast. The halo timer is ten and bedtime or is 40 at GNC will be automatic and there will be the RBD. And non broadcast the halo time or increase 10-30, deadtime or increased 120. And the agency is not automatic. You need to put them. You need to tell them that this is your neighbor. There should be the RBD are. However, end point to multipoint the timer is therapy 10-30 from date-time are as full G21 20 agencies are two metric. However, there is no DRP, DR, no need of beer video. Similarly, point to multipoint broadcast. The timer is 31, 20, the neighbor ship has to be manual and ODR video. And the last one is point-to-point, which is 10.40 and automatic and no DRP, DRS deer. So we're going to see are these and the lame. Let's discuss the first one. Point-to-point network. Basically, point-to-point network means when the devices are connected through CDN link, not directly the Ethernet or gig interface or ten gig interface. Those is called broadcast network, not point-to-point. Keep in mind there is a difference. So point-to-point link, you know, a senior link is not anymore in all deserts has to be available. You need to connect the devices through CDN link. Maybe you remember some of you, if you have a serial interface, it used to be. If I have some weird, even we are not teaching anymore and CCNE at this one, like this one, but not this one. Need to show you the proper one, Almost like this, but let me type the serial cable, Cisco router. It used to be like this, to connect almost this one. Yeah, this end is this, but this n is a bit different. This one is okay, CTE and BCE. It used to be like this. One is to connect it to the ISP and other one is to use a router. This was called a serial link. It's not anymore by the way. So the one which I'm talking about one-to-one is this CDN link, not the one which you are using Ethernet Fast Ethernet gig interface. Those are coming under the broadcast. Okay? This was the simplest form of the network type. Point-to-point and two-point are connected with each other directly. And they are connected through serial link, which I told you the SDLC and PPP. Normally, an old days we need to connect like this. Maybe in some places you're going to find out now as well. Maybe in some countries. Now, if you have a point-to-point, so what will be the thing which we can gauge? Ospf does not select the RBD. Because if two people are working and you say lets you become a team leader and I become what is called tRNA, become obese if you are not available. So I will be the team leader. It doesn't make any sense to people and you are using okay, you are team leader and let's go to manager and discuss because two people are walking into personnel working, just go to manager directly and you can discuss no need of DRP, no team leader. So the same concept you can apply here to devices are connected through serial links. So they will not choose any DR. BTO, which we'll discuss. Because no need. And what they will do, they will send the packet through multicast two to 4005. So remember, serial link of two devices are connected, so we call them point-to-point. They will not select the RBD or we will see in the lab. And they will send the Hello packet to do 4005, which is the multicast IP. And the halo timer will be 10 s and the dead timer will be 42nd is we know the normal one and they will discover the Niobrara automatically. So we need to remember five thing. They will not choose DBDR. Hello will be through multicast. Hello packet will be after 10 s and the timer will be 40 s and the neighbor will be automatically, they will find the neighbor and discarded. Automatically. Done. This is called point-to-point. We're going to see in the lab. This is point-to-point. They are connected through serial, so that one we will assign to R1 and R2 we're going to assign to do and we will configure OSPF between these two router and then from the CLI command and also from Wireshark. We're going to see that the areas are the RBD or not, and how they are sending the Hello packet and how long they are sending 10 s or 30. You will verify in the lab. This is the first way to configure SPF and point-to-point network so they behave differently. Now coming to broadcast network, even if you connect two devices through Ethernet link, they are also coming under broadcast. Either the gig interface is still there. Coming under broadcasts. A network tag that connect two or more OSPF router with each other. And Ethernet subnet. We call them broadcast. Now in the broadcast, again, the first thing we need to remember, they will discover neighbor automatically. And then we'll send Hello packet and multicast. Unicast is through multicast. Yes, but only one thing has changed. There will be a DRP because we have a broadcast network more than one router. So now we need to choose a DRP, DRP and the halo time, whereas 10 s and the timer is 40 s, same like a ball. The only difference is DBDR is there. And this is most widely used network type you may see to send and receive multicast and broadcast transmission. So we have a switch here or maybe any other thing We are connected. So in this case, they will use multicast sender to send hello. And hello will be ten second and 42nd, and there will be DRP, DR. So second type, third type non broadcast network. Now a similar like a broadcast, but here the device is not switch. It may be a Frame Relay are some others. Now they are not directly reachable because the air is or device is not as switch to broadcast and they can reach to each other. The first thing we do, we're gonna face and non broadcast network when we configure SPF, no dynamic neighbor discovery. This is the first thing we're going to face. And we need to configure the night shift statically. And OSPF is possible to configure night, but statically, Halo will be sent through unicast because in broadcast network they use multicast to send and receive hello. Also the halo become more, it will become ten to 30 32nd and deadtime are far from 41, 22nd. If you have a network, non broadcast network and and it required the RBD are so DBDR will be there. Now this type of network is also not anymore and real-world it oldest frame relay was used. Now there are many other technology available so which replaced the frame relay. However, some organizations still using frame relay. Their case if you have branches and they are connected through frame relay. So now in that case, you have a non broadcast network. So if you configure SPF, so don't think that the Halo will be ten second because this is in our mind that whenever we configured with SPF, so the timer will be TNC can know. And we're thinking that because we configure SPF, so the neighbor ship will become discovered automatically know you need to configure statically because the network type change. So you get the idea. So if the network is changing first, you need to find out which type of network they type of OSPF you need to configure. That's why we call them OSPF network type. Which type of network you hail, then the OSPF will behave differently. If you have a AGRP, no worries everywhere the same configuration. If you have a rib configuration, every beer, every type of network, you need to configure the same way. And the similar IS-IS. But if you have a OSPF need to configure, which is widely used 99 per cent. You're gonna see OSPF in the real-world, not EEG ERP. Because normally you have a router, other vendor router which do not support EA GRP. Also, AARP has some disadvantages as compared to SPF. So that's why it means is for sure that every week you will see OSPF. So when the network is changing, so the behavior is changing and you need to know the behavior because you're going to, okay, suppose you have this type of topology and somebody told you, okay, configure SPF configured with people, it's not working. You should know this What I know, you need to type network and dense wildcard and then the area we configure everything. I don't know why it's not working. Because first you need to understand which type of network that is. If you know this one, you need to configure static neighbor shapes so the neighbor ship will come up. Then you may be thinking that there should be, the timer should be 10.40, which we know. But when you check the timer is different because the network type is different. So that's why we are discussing these things. Now coming to the other one is non broadcasts multi-axis. Now in this situation, they will choose DRP, DR. And then I bought you will be again manually. And the timer will be 30-second and one 20-second timer is almost similar like the above one, but few things are different. And finally, we have another one point to multipoint. Again as similar like above. But this time we don't have a broadcast network. Neither we were non broadcast network. This time we have a point to multipoint connectivity. It's like a point-to-point connection. You have R1 to R2. Point-to-point, R12 are three point-to-point R2, R3, point-to-point, R3 to R1, point-to-point. So you can say like this. So we call them point to multipoint. Now, if you have point to multipoint connectivity, so there will be no DRP, DRP election. That's the first thing. However, there will be automatic discovery. And the previous one there was static configuration. The timer is same, 30-second, one, 20-second timer. It's increased. The above one. We don't need the RBD are because we need to see the Ababa to you. Which thing you need to check. Hello timer, deadtime. Our agency as manual or automatic and the RBD are, is they are not dictate end point to multipoint. Know the RBD is there. This code here is automatic and timer statistic into one 22nd. And I believe I did not write they will send the packet, Hello packet through broad to multicast. That's it we will see in the lab as well. So these are the different network type when you configure SPF. So first you need to find out which type of network we heal. Then you need to understand the same way to configure SPF. I hope so you get the idea. Now in the next lab. In the next slide, we're going to see the lab and we will configure different network type and we will see the behavior or OSPF. 20. OSPF Network Types Lab: Okay, so in previous lab you discuss theoretically different OSPF network type. So let's do one by one. The first one we're going to see point-to-point network. As I told you, point-to-point network means connectivity through serial interface is not through the Ethernet interfaces. If you configure them through Ethernet, so it will become a broadcast, not point-to-point. Okay, So this is our first one. So let's see. The first one is here. I have two router and I connect them to cereal. I will show you if you have a router, suppose you need to use this router, by the way, Cisco IOL, when you go to layer three. So I use the first one, this one, L3, these are the layer two and layer three switches. You need to come here, this one, L3, and this is the router. I take this router. Okay, Sorry. Let me show you the serial link because by default CDN link is not here. So I just wanted to show you if you face such issue. So when you open it here as Ethernet, and beside here is right, serial, just type 11 is enough for you. One means four. She didn't interfaces. So if you tried to connect, now, here you're going to see an R1 just to show you, I don't want to connect. And here is the CDN one slot 01,112.13. So when you type one, so it will show you for serial interfaces and you just need one. So keep in mind this is only available in IOL, not in the other router. Because up to now we are using this router. Let me see us are not available. If you go to this router, the one which we are using, this one. So if I choose this one, I believe there is no Syrian. You can see ethernet only in the Ethernet means that gig interface is here, but there is no serial coming. So it means if you want to perform this lab so you need to change the router. Also enter the same one model router. This one, I believe is also not available in this one. Slot one and slot two. Slot one only Ethernet interfaces and also Ethernet interfaces. So you have only one choice, IOL router. So that's why I use those routers. Just to tell you, by the way, you will get this topology, is this important? It will start work because you already have this router. Let's start at one first. We want to do the first one point-to-point. Again, I'm telling you it's connected through serial. No, because nothing is configured here. And let's open our two as well. So no configuration is the R1 is open and R2 is open. I will apply the script because now you know how to configure a router is OSPF. So first we need to assign IP to CDL Once-ler zero to delta two and apply IP to one slot zero. Okay? So let me go here. And point-to-point, I don't know where it is point-to-point here. So the CDL Once-ler 0122, That's it. So let me go to enable copy. And so I changed the name to R1 and assign IP to see the interface. Let's move to our to Israel and R2. R2, D2. Only. Ip is different. And now the OSPF configuration and Jay-Z, it's almost same on both router, router OSPF network because you have just this interface which is directly connected. So 1921600, wildcard 0002550 and both router, it will be the same. So I need to assign here and similarly here they all connect duty is there. After a while there will be an agency which we already discussed in OSPF and they are loading from full to loading. We already know now what is the status you remember? So they will go they will become an I, but after a while and then we will verify a few things. And those things, which we'll discuss theoretically, this is point-to-point connectivity. And now let's open both the router and see. I believe we can figure this one. And these are the command show IP interface to find out the detail. Let's go to show ip OSPF interface Syria once let zero. So here we need to find out the network type is, here is network type point-to-point, which we discussed the first one. Let's go to the theory again. And let's see one-by-one. So point-to-point. Okay? So if we go back, so they said the network type is, this is our topic. Network type is point-to-point. What we discuss next, the, they will send the halo packet through 224005. How we know we have many choice. Wireshark is we'll and debug eye pupil SPF. Hello. Let's see which IP they are sending the hello to the other router. Here is they say, I'm sending hello through 224005. So this one is done. You all. So two things has been verified it and point-to-point, They are using multicast address two to 400, 5% hello. Now, this is point-to-point. We also verify this one. Now let's see, they will choose DRP. Dr. we need to find out that show IP OSPF neighbor. And the neighbor in this state. You remember here they will choose the RBD area. Here. No. Let's see from another way, show IP interface Syrian one slave zero. And let's see the result in DRP, DR. So there is, there, we'll mention here somewhere if they have already or BGR. So it's not mentioned here either. If you type show IPO SPF. So here you will find there is no glue related to the IRB DR. And if I go back to IPO SPF interface, the third thing I need to verify that the Halo timer, so if we say 10-second and 40, let's see. They say that the Halo will be ten second and dead time or is 40 s. Okay. There is no DR. video mentioned anywhere. When we do the next one, you will see that there should be the VTR. Okay? What else? If I can verify from other place? Let's go back. So the neighbor detail and debug, I show you the, okay, there is a command. Let's see this one. If we can see more details. So R1, so again, there is nothing, okay, priority, this is full status and hello. And let's see. I don't think we can see anything from here. This just the night, but it's told R2 and there is a dead time or do and 39 s and night but is off, this is the uptime. So we can not see anything from here, but at least from here we can see that the halo timer is ten, deadtime or is 40. The network type is point-to-point. And also they will use a multicast address to send and receive the Hello packet. So they tick. So now we verified the first one. We saw these details related to point-to-point. Let's move to the broadcast network. And let's move to here in the lab. And did not start the white shark for some reason. If you have a serial link, so in Wireshark they will never capture. So what is the seedling Once-ler is zero. So if I go to one slot zero, it used to be in because previously I used GNS3. So it will was recording. There's this screenshot is from my GNS3. I try here, then I searched it not showing anything you see on the CDL. On the other one it will show you, it will never show USPS. This is just the layer-2 connectivity detail for some reason. So that's why I cannot show you from Wireshark only in this case. This part is done. Let's right-click and stop this one. And now our target is the second thing. And the second thing is we have a broadcast network and we need to verify few thing in this one. Here I created a broadcast network. Basically let me send this one to pick. There is a switch just I put a cloud input to make them good impression otherwise is nothing. So basically these three router are connected with the switch. And R1, we're going to assign one dot one dot 2.1 dot three. And then we will advertise with SPF, same OSPF, we will advertise and L3 Router. Let's see, because they are in the same network. So let's go to R1. Nothing gets configured here. And let's open up to Israel. And nothing is configured there. And let's move to R3. And they are connected through switch. Okay, So this is called broadcast network. So let's go to R1. And let me clear all do as well. Let's create our three Israel and let's go to the broadcast networks. So we're going to assign Ethernet because this Ethernet wondered one, Ethernet wonder to Ethernet one dot three. Okay? So it's so simple. I hope you understand this one. They try and copy paste. So R1 change the name and assign the IP address, or to change the name and assign IP address. That's a simple things I'm doing. So it should be R3. Let's copy and wonder 31.1.1.1 dot 2.1 dot three. And the USP of configuration should be the same on all three router R1, R2, and R3, because they are in the same network and we just advertise the network and areas zero. So let me copy this one. And let's go to our one. Same way SPF or two same OSPF and R3. And after a while they will become neighbor until they become Nivre. Let me ready to the enable mode. So after a while they will become a neighbor, going to take some time to become neighbor. Okay? Okay, there is one more thing, no CDP run because switches in the middle, so they're going to make an issue. So let me know CDP run. This is just not to show you that error that they're going to show you after a while that there is no CDP run. And now I am ready. So this become loading and they become neighbor. If I say show IP OSPF neighbor. So they have a tonight but now, previously there was a day. Now they are choosing because they're held to select a DRP until they become up. Let's go back to the theory and broadcast network. We say the neighbor will discover automatically, yes, their Discord and I bought automatically, it's here. They say I have two Nippur. One point is clear. Second day gonna use multicast address two to 4005 to send and receive Hello. How we can see that one 2-way a debug IPO is P of Halo. And let's see which IP they are using to send. Yeah. So not yet because they just received the hello. Yes, it's here. So are sending the halo and this one, n u n, We can verify through Wireshark as well. Let me capture and previous one. Wireshark was not working, so that's why I never show you. But here it's working. So let's see. And we can verify from Wireshark as well. The same thing which we discussed theoretically. So here we will see 224005 and let me make them SPF only. It's here and the IPS two to 4005 and multicast IP done. Let's move to the second thing. Is there any DR. video? Yes. Let's check out the RBD or show IP OSPF interface easier to play zero. And here is first, let's see, the network type is broadcast. Previously. It was point-to-point assuring that the network type is broadcast. So you can use this command to find out that which type of network it is, which type of power is P of network? You can find out from here. And let's use the RBD or so. There should be designated router is here, there should be backup designated router. Here you can see the RBD and previous one. This command was not available to things. So let's go to Wireshark is well, if I open, there should be the RBD or detail as well. And if I open OSPF Hello packet, we know those periods. So here is the UC, this one designated router and backup designated outer one dot 3.1 dot two. You get the idea. So it means two things are available. So we vary by a verified date. They'll learn the route automatically dynamically. Headway send through multicast, be RBD or is there. And let's find out the halo and tech timer. So it can be very far from here as well. They said the halo is ten and deadtime, whereas 40, and we can verify from Wireshark, Israel. Whereas this here, hello interval is 10-second and date interval is 42nd. You can see both from here as well. So now this has been proved that in broadcast network, they're going to choose the RBD and discovery will be automatic. Then I brush it will be dynamic. And they're going to use two to 4005 to send and receive the halo. And also the halo timer will be 10 s and the timer will be 40 s. These five thing we need to verify basically the halo timer, the timer, the RBD election, which IP they're using to send and receive the updates. And finally, the naval ship is dynamic. Either static, we verify five thing and broadcast network, and that's it. And it's here by the way, we are doing lab. But just to show you there, from here we verify. The network type was broadcast, the RBD or was there Hello Austin and ten, and we verify from what shock is. Well, now let's move to the third one. But for that one, I need to stop these. I don't need this one now. Let me stop this one. And also let me close. And now let's move to the third one. The third one can be used for many purposes. Let me send this one by the way, too big. It's basically switch, but I changed the icon. Okay. Now coming to the final one, this final one we're going to use for our purpose non broadcast network to make them our frame relay, switch. And point to multipoint just to type one extra command to make them point to multipoint. The same topology will be used for two different network type. Okay? So what we need first, we need to open R1. By the way, nothing is configured here. So now let's move to R2 as well. No, let's move to our three as well. No, it's not open. So let's three or three? No. Because first time and this is a router by the way. Frame relay switches also a router, but we will make them as a frame relay switch. We will apply some configuration. So we're going to make them as a frame or less switch. So let's go to our one and make them ready. And let's go to R2 and clear the screen. And let's move to our three and clear the screen to make them ready. And also basically this is also our outer frame relay switch. You can make don't need to be a friendly. It's not the part of the course. We need to know the network. So don't worry, we're going to make them friendly. Let's switch. The configuration is here. You just need to copy paste. It will make them a frame relay switches here. So let me copy this configuration. You don't need to understand it is basically frame relay is not anymore. So this router, I say the host name is frame relay switch enabled frame relay switching. And this the interface zero slash zero, this one enable threshold, the clock rate and the serial interface. We do this one. Julius not anymore serial interfaces. I said this is DCE, there is duty E and D, C interfaces and old days. And then I've configured frame relay here. And similarly in the second interface and the interface, there are three interfaces. So let me copy this configuration. You don't need to understand it and they're done. So we don't need this anymore. And let me close frame relay switch because our target as these three routers. And now let's configure the basic IP configuration. So what I need to do, I need to copy the configuration of R1. R1 is the serial zero slash zero or two is also a CDN zero slope zero in our previous serial zero slope zero. So here I need to assign IP one dot one dot 2.1 dot three. And also the SDLC value, again is the outer scope things. But anyway, I will assign. So what I need to do, an R1. I believe this the things I need to do it yeah, it's correct. So let me copy this one and change the name and configure IP and frame relay and similarly R2. Okay, and now let's do the third router is when. Okay, so three router configured. I hope so. And now I need to configure OSPF. So let me copy this one. Here is now the IP addresses are configured to do a show IP interface brief. This is a serial interface and IPS configured similarly. Do I configure one, that two, and similarly R3. Now in previous case what we've done, then we configure OSPF. Yeah, let me do the same thing. Here. There's router OSPF or 92.60, 81, and this is a wildcard, and so on. And let's do it here. And let's do here. This is what I've done in previous case. Yeah, Let's do they will become neighbor or not? No. Let's see. Because I can figure the same thing if I say sure, running section OSPF, this what I done, network 1.2 because they are belonged to the same network. So I advertise them in areas zero and there has to become neighbor. Because we did in the previous case and they become a neighbor. But we are doing another type of network which is non broadcasts. So N broadcast network. What will happen? Let's go. So now you will see a non broadcast know dynamic. And I bought this Cody. If I go to broadcast, their neighbor are dynamically discover the same configuration. However, there is no neither ship coming previously. We wait for awhile. Let's see. Should I be OSPF neighbor? Yes, I don't have any neighbor. Even though we configuration is correct. The reason is no dynamic and night but a discovery. Hokey. Let's see another thing. Show IP interface. She didn't zealously zero. Okay, So the network type is the non broadcast and previous it was written broadcast. If you go back here. So in previous case when we discuss here, it was written broadcast. But this time we are doing non broadcast because frame relay in the middle, not the switch in the middle. The network type is change. And if Tony prototype has changed, so if the network is a non broadcast with chewing here, from this command, you can find out if the network type is non broadcast. You will tell to your colleague that, okay? Because the network type is non broadcast. So there's OSPF configuration is not enough because we need to configure static neighbor. You get the idea. You need to tell them that because this is a non broadcast, so it will not work. We need to configure static night, but shape how we can configure static membership. So we need to go to configuration router, OSPF, and the first router, router, who is PFK-1. And here I need to type neighbor that my neighbor is one DR2, which is U2, and my neighbor is one dot three. This extra command you need to type. And similarly an odd do. You need to go to router OSPF? One and you need to type night but 1922168, one, that one is my neighbor and one dot three is my neighbor. And similarly in R3, you need to go here, router, OSPF one, and you need to type the minor but as 16081 dot one, R1 and R2, R2 and R2. I say here when I bought 131, I say my name, but it's 23.3. I say minor, but it's one to every router. You need to tell them who is your neighbor. Because the network is non broadcasts and non broadcast, you need to type these extra command. This is called configuration of static sniper ship. Just this command neighbor. And now if we check, So previously I say, I don't have a neighbor. If I type command show IP, SPF, sorry. First I need to check the nipper. Now nobody has come up. But the good news is there is DBDR is weird. Let's check out the theory that there will be the RBD are. So the first thing we verify that no dynamic discovery and you need to configure static now. But if we'd done this one, then the Halo will be through Unicast. Okay, this is a new thing. If I say Debug IP, OSPF Hello. So previously it was sending through 224005 that when large B anymore in the case you see as a one dot two is sending to one dot. One dot three is sending to one dot three. Hello has to receive and send. You get the idea there shouldn't be two to 4005 anymore. This unicast because I cannot capture let me see. I don't think so. It's not working. I Google it. Also people say that no, it's not working. Wireshark when you are connected through serial. Otherwise, I can show you from year they will use their Unicast addresses, not the multicast to send and receive. Even if I on, I don't think so. It's going to show but just to maybe let me see again. I don't know. It's not showing I know is for sure. So let me quit. I can show you from here. You can see as Unicast. Okay. So you get the idea, you all to undo bug. Yes, we verify that the halo is not anymore through multicast. Two to 4005 used to be previously. This one is not in this case. Three thing we verify dynamic disk Cody was not there. We configure static neighbor sheep. We verify the halo, ascend through Unicast. Now the timer. Let's see what is the timer so far the timer, what I can do enable show IP OSPF interface series zero plus zero. So now we know the network type is non broadcast media as dear as a good news day, they choose DR. beauty or designated and backup designated. And yes, we can see the halo is increased 10-30 and dead timer is increased from 41, 20. You get the idea. So get this thing is also verify. What else? Yes, DR. Bd or SPLV verify these things. And the final thing we need to verify, okay, So this was non broadcast network. And we solve from here is non broadcast network. Okay? Now final one is, let's go to the lab. By the way, none broadcast. So we configure this one. This is frame relay configuration, and this is the static neighbor ship. It is important in this case. And then we verify from here. So it was not broadcast, DBDR was there. Hello Enter timer was more. And we can also verify show IPO SPF neighbors. So see the DRP, DR. And the Hello packet is through Unicast. And finally, we have another wind to multipoint the same topology can be configured as a point to multipoint. Only one small changes we need to do. Under every router interface, we need to type this command. I do SPF network. So we can make the non broadcast network is a multipoint broadcast here. Similarly, if I type this command and other router as well. So if I check here, so it's a non broadcasts and similarly an R3. Sorry, Start live it and it's your non broadcasts. How we can make this non broadcast is a multi-point. So go to configuration and I believe it's under the interface, this command under interface cereal slash zero, I be OSPF network. And if you type a question mark, so there is a broadcast, there is a non broadcast, there is a point to multipoint, and there is a point-to-point. Point-to-point we've done, we've done not broadcast, we done a broadcast, but we want to test multipoint so we can make them this topology multipoint, point to multipoint and done. Okay, and I need to type this command under R2 Israel. And interface seriously zero and apply this command and similarly or three zeros, zero interface and apply this command. Now, what will be the difference if you make them point to multipoint the RBD. Otherwise, it will be not anymore. There will be automatic discovery. It means I don't need the static route anymore. So let's remove. Because they do discovery will be automatic. So if the discard is there to metric section OSPF. So in the previous case when it was a non broadcast, so what I've done, I type night but let me remove that neighbor router, OSPF one. Because they say I don't need static neighbor ship, Let's remove them. And remove from here as well. They say that in the case of multiplying Nu need upstairs neighbor shape. Okay, so let's delete them. And here as well. Router, router, OSPF, SPF one, and the the at night but our tonight but was one and our tonight but was three. So I remove them from here. And similarly, Router OSPF. Ospf one, no, the neighbor was two years N1. So now sure. Running section OSPF, nostalgic neighbor, she pays deer. And the IPSP IP network type is point to multipoint how I can see. So show IP OSPF interface zero slash zero. And here is, now it's written point to multipoint the same command if I apply an R1. So previously it was showing differently. Now say point to multipoint just before when we check it to us and none broadcasts. Now, because we changed the behavior is say point to multipoint. You get the idea. And when it was non broadcast. So there was DRP TR and witnessed become blind to multiple ones. So no DBDR is not showing any anything. However, when it was what was it was non broadcast. So the halo was ten, ended timer was 20. So it's the same. This what we see. So if you go to theory part again, they can point to multipoint node your video. Previously it was yesterday's code is automatic. How we know less checkout shoe, IPO, SPF sniper. Yes, I get the neighbor, but there is no DR. BD or they're set. The shear and the timer is the same and the network is point to multipoint. And what else will be changed? Yes. 32nd and one-twenty was the same. It was previously as well. But we're not sure the Hello packet. So let's verify that one debug IPO SPF, halo, which is two to 4005. And previous case it was unicast. So let's see. Here is notice the first one they will send to. And after that we can verify. Let's see. You asked us unique us by the way, maybe are not mentioned. So let's see one link, but the USP picket work with multicast. Here I mentioned multicast and started yeah, sorry. Yeah, it's true multicast. Okay, So two things is being changed from non broadcasts to multipoint. No need of static membership, no need of DRP, DR. And what else? The halo packet was unicast now is become multicast. And you are, we are done with this topology as well. So that's it. Any theoretically and also practically let me go. We change the I plus point to multipoint. And this the we remove the neighbor ship. Strategic leadership is not required. And then we verify. So this one point to multipoint. Hello timer and ODR video. Here is the dash, dash, no DBDR, and the packet is through multicast as well. And that's it. These are the different types. Let's go to the theory and the top. These are the main thing you need to verify. We saw the halo was ten and the timer was 49 Budweiser to metric DBDR was there indicates a broadcast. The case of non broadcast reconfigure the membership main valley and the RBD or was there when we make them point to multipoint. So the timer increase 103120. However, the neighbor ship was or two matrix, but there was no DLB. Dlb just done this one. The point-to-point know DR. video was there and the automatic. Okay. That's it. So far one Lavy used to this topology for two different purpose. So that's why I return non broadcast and also point to multipoint. I hope so you get the idea that OSPF network, that's it.