Hello this is your host Habib's Korea. In this lecture we are moving towards actual simulation for for the topic that we have discussed which is the LSA types and we will discover the OSPF link state data databases in in in all of these routers that we see in the topology but mainly we will examine our two because that's the backbone router and we will see we will see the OSPF topology from from our tools perspective. So, so as you know we discussed there the LSA types which is type one which is the router LSA type two network LSA type three which is the summary LSA type four which is the ASB Our summary of essays and type five, which is the autonomous system lsaps. Now, just just a brief, no How about this topology, as you can see we have we have r1, which is acting as an ABR because it's connected to area zero, it's connected to area one.

And similarly it's connected to area two. So it has three interfaces. And each interface is connected to a different area. Our four here is, is acting as a SVR. The reason is there's an external network that is connected to to our four and and let's move on to configure the topology based on the subnet that we have already provided here. We will create some loopback interfaces definitely, like in our five we will create one loopback interface, our one will have one loopback interface and our two will have loopback interface, our three and our four I don't think it's necessary to provide a loopback IP address.

But let's, let's start it's gonna be fun. And hopefully we can get this topology up and running in in the shortest time possible. So let's start with our one. Okay, so I am in the console here for r1 and we will start configuring the interfaces first. IP address 172 30 dot 12 dot two to five to two subnet mask would only give us two hosts interface as the slash zero IP address 172 3213 dot make it two as well. We will configure a loopback address as well.

IP let's let's take a loopback address to be one dot one. And we will also add the deal the router protocol. So, router OSPF one router ID and then we will also add the networks. So the first network that we want to add is the 172 dot 30 dot 12 dot two now that's an area zero Network 13 dot two and that scenario one and that's an area according to our topology and we do have a network which is 192 dot 16 dot 101 in area zero. Let's save it. So r one is configured.

Let's go to r two. Let's bring it up and bring up the console. So similarly r two is up here and we will configure the interfaces interface loopback zero let's give it an IP address of 192 16 dot two dot two. interface FA zero slash zero and the IP address on this end of the router will make a dot one 172 two dot 12 dot one no shut. router, OSPF one. We have two networks here which is 192 dot 16 dot two to zero dot zero dot zero area zero and another network which is the 172 30 dot 12 dot one here is zero.

And we can see the OSPF has formed an adjacency This is great. So the first so, so we have configured that now. We could do actually we could do show IP route. And we can see there's the topology here, which is the there's a route here which is oh and that's the OSPF route that I have here. That's going towards That's getting advertised via 172 30 dot 12 dot two. Now if I look at the show IP, OSPF database, I can see there's a there's a router ID, which is one dot one dot one in this area, it's advertised here and then there's 192 16 dot two dot two which is advertised by r two.

So this is actually a type one link state advertisement here. You can see that but we will get back to this in a shot and shortly, but let's configure first the topology and then we will discuss further about the link states. Okay, thank you. We will be moving now to our three and the Let's wait for the console to come up. Okay, so just logged into our three and let's configure the interfaces interface zero slash zero IP address 172 dot 30 to 30 dot one no shot and let's add a router OSPF one network 172 3013 81 less safe now we will move on to are for. I'm here on our floor right now and we will configure the interfaces as well.

So interface serial zero slash one IP address 172 dot 30 dot four to 1-255-255-2552 252. No Sure. There's another interface here for our four which has the IP address of 172 dot two dot 45 dot two to five, five to 255255225 to no shot Show IP interface brief I just want to say the interfaces are up. Great. Let's add the routing protocol network 172 that 30 dot 14 dot one, area two. So our four is basically as soon interfaces one interface in area two and the other interfaces and an external domain which we will not add it to the OSPF here but what we can do in our four is establish a static route So IP route, we will we will try to reach to the loopback address of our five.

And we're assuming the loopback address is is, is an IP address somewhere outside and an external network and we have to reach it somehow. And it's going via the interface and Justin to our force F Zero slash zero. So it's 172 to 245 dot one In consistent address, okay, so that's good. Let's save the topology, the configuration for our four. Okay, so if I look into so we added the OSPF inflammation we added the static route to the neighboring device and let's jump to our five Okay, so I'm here in our fight over to the same thing we'll configure first interfaces so interface fa, zero slash zero with the IP address of 172 dot 30 dot 45 dot 125525 Five to five, five to 250 to no shot. And we will also configure the loopback address that we were talking about.

The IP address is 100 100 100 dot 1255255 to zero to zero. That's the IP address and no shot, exit, exit. So that's all we can do in R five, we're assuming it's an external network. We cannot add anything to it and we don't have any access to it. But for the purpose of the simulation, we're just giving it an IP address a loopback IP address, so that we can actually our four can reach it. Let's go back to our four And let's see if our static route that we created can actually reach it.

So so we are here in our for let's try to ping 100 100 101. And yes, we can ping it. That's great. So our static route that we added is, is good. Now, if I do show IP route here, there's a static route and there's the directly connected route. I wonder why I'm not seeing the show running config.

Okay, so for some reason we're not able to see the neighboring or any adjacency that's forming in our four. So part of it is really to troubleshoot what the problem is. So we fixed one side of the r four which is getting access to the external network. Internally, it's not working. So the one thing I noticed is we have not assigned it on the router ID. So router OSPF one and let's assign it a router ID of four dot four dot four dot four.

And once we do that, and we exit that and let's see show IP interface brief I just want to make sure that we are actually the issue is the serial interface s zero slash zero is showing protocol down. So called t interface as zero slash zero. shot, no shot. And if I go back and I do show IP interface brief and still it's showing protocol down. So Oh, I see I know what happened. It's not actually we're supposed to configure as zero slash one not as zero slash zero.

My mistake. Let's go back to interface s zero slash zero and do no IP address. Address 172 dot 14 dot 1-255-255-2255 2252. And it's best to shut it down. And let's go to interface s zero slash one IP address 172 dot 30 dot 14 dot 1-255-255-2255 2252 IP address, no shot and that should be it. And yes, I can see the interfaces coming up.

One thing we need to do probably is to Yes, so we had to wait a little bit to get the adjacency and the OSPF database formed. So if I do show IP OSPF I do have routes here show IP route OSPF. I do see it okay so as you can see right now in the show IP route OSPF I don't see the network 400 100 100 dot one but I do have it in my I do have it in my routing table. As you can see I do have this this network in my routing table but when I go to show IP route or show IP route OSPF I don't see it. Okay, one way to do it is to really redistribute that network to OSPF. So, the best way to do is if you go to and pay attention to this because this is really important in in the real world.

So if you do come T and you do router OSPF one and I do redistribute, right. And now I can do static statics subnets Yeah, so that's all you need to do actually. So get it into the show IP show IP route. So we do see it here, that's fine. And we did add the redistribute command into our four. So that should inject our route into the other routers routing table.

So let's, let's now go ahead and look at our two and just investigate the data link. The link state database basically so let's go ahead and do it step by step so we can Okay, so the basically the first command that we will do to investigate the database or to check a database Is the show IP OSPF database. Now the database will have information about all the LSA and that will describe the network topology from this routers point of view. So if I do show IP OSPF, OSPF database. As you can see, I have two database here that's created. And I do see all the networks, right and now we will examine all these networks in the database.

So basically, if it comes to the type one LSA then this is the LSA four type one there you go. And it shows that this one is also type one LSA okay which is also known as the router, router LSA Okay. Now if I also do I can do show IP, OSPF database router self originate, I can see what this router has originated in the topology so it says router link state that's the link state which is the router link state which is type one and this is the link state ID which is basically the the loopback address of the IP address of the router. This is what's advertising and it's connected to a transit network, which is the area zero network here also shows it's an area zero network and the link ID of the designated router to Dr. Is this one 172 32 after two and the router interface that it's going through is this one.

So that's all about the type one LSA. Okay, so let's go back to the to the database itself again show IP, OSPF database. And let's talk about the type two LSA which is known as the network LSA. Now the network LSA is when you look at it, it will be in this area, this area of the database and it will tell you This is the advertisement link it receipts for type two LSA. And that's the other way you can actually investigate type two LSA is by typing show IP OSPF, OSPF database network and you will see exactly the same thing. You will see the link state ID which is the IP address of the designated router which is that and you will also see the advertising router which is the router ID of the of the designated router and you will basically see the details in in a clear picture so, If you basically say if if you want to know what which routers to do so if I do show IP OSPF neighbor so this is the DR one dot one dot one dot one.

And the reason why this became the DVR is because the loopback IP address that we we gave it was one 192 16 dot two dot two. And because it's higher Actually, we gave it 192 16 dot one dot one right. So, this is the, this is the DVR that it shows. So our one is the DVR and it's also the A ABR of the of this topology. So according to the topology, this is the result that we received. Yeah, so.

So we were discussing about the DR here and how did it Find how the r one was elected as the Dr. And the explanation is the interface IP address, which is F Zero slash zero of r1 is higher and it's given 172 dot 30 dot 1230. So that dot 12 the two that's the IP address and that is the reason why this was this was given designated router the role okay. So similarly we will check our one as well and see if it corresponds to the same. So here we are in our one and if I do show IP OSPF neighbor I can see there is the BDR which is actually pointing to a 192 16 dot two dot two with the IP interface of 172 30 dot 12 dot one. And that's a BDR. So in summary in one area, if you have multiple routers in that area, there will be a DR and a BDR.

Election. And that's how that's how this is, this is being these routers are elected for the roles. The interesting part is when there are many routers, they actually talk to the they actually talk to the BDR. And the BDR talks to the Dr. Dr. talks to the BDR. And then the video will again transmit the the updates to the other routers, that's how OSPF works and that's how it convergence is literally It's faster than the other routing protocols. And also because of the areas that helps a lot because because of the areas this scalability is better, it's it's, it's scalable, it's faster, and so on.

So we covered type one type two LSA. Now let's go back to the show IP OSPF database again. And now for the summary basically, which is the type three LSA. This is the area of focus for type three LSA, which is the summary. And the summary is basically provided by the area border router, which is, in this case, area border router is r1. Because it's it's basically connecting all the areas together.

And what it does. r1 is basically taking the information that I received from area one, area two, and it summarizes it and then passes passes it on to r two, and r two sees it in this area of the database. I hope this is clear. You can also see the type three LSA is by just typing. If you just type show IP, OSPF database summary, this is a good command to understand the summary the type three summary. So you can see there's this network here with the link state ID of the network which is network 172 to 30 dot 13.

And there should be another one as well which is this 114. This is the summary. Okay, so now let's move on to the type four LSA which is basically the advertisements for the external routes. So if I again go back to show IP OSPF database, and in here I can see there is a summary ASP link state which is coming from this router ID, which is our four. So in our topology, our four is the one that that's that's injecting an external route into the OSPF and you can see here it's coming from here to the area border router. And the external link states are here hundred 100 dot zero.

And it's shown here. The other command we can use is show IP OSPF database and I can put is br summary. And there you go, this is going to be the D. This is going to give us all the details here. And it's it's a command that makes things easy to understand what's going on in the network and what is the external route coming from. So this is the command that we will be using mostly. And the last one is the type five LSA which is the external LSA is.

Again, it's related to a ISP or router. So if I go back again to show IP OSPF, OSPF database As I stated that dot one is basically the last type five external, there you go type five external link states and if I type show IP OSPF database external that should give me the detailed information about what is there as an external link. And there you go, that's the link state. It tells me it's a slash 24 network mask. That's how we actually put in our static IP route. So we gave it slash 24.

So I hope the end of this topology and this lab that I have demonstrated, you have enough knowledge to go ahead and and investigate and create OSPF network on your own. I believe this was the last chapter of OSPF that I wanted to cover. And it's been it's been great teaching this course. OSPF is a very big routing protocol and it has a lot of in depth information. It can be used in many ways. We have covered the technical aspects of OSPF in a real world environment.

And this should be quite good in giving you information about OSPF in practical world. And I hope you have enjoyed and see you soon again in my next topics or courses that I will be presenting. I hope you can join me in those courses as well. Thank you again and have a wonderful day.