Hello there, this is your host Habib Korea and I am going to start with chapter five which is in this topology which is topology number four I will be introducing BGP back door basically in this topology as it states under the tasks to complete number one it says complete the topology and assign the IP to all the interfaces. Basically we are assuming that these are three sites and each site has a different autonomous system as you can see, and and all the external interfaces for these routers. We will run rip protocol on all the interfaces serial interfaces. We will run What do you call AIG RP between our four and our two big Basically I'm assuming this is a this is again an internet cloud or a when topology that's given by an ISP and we are trying to connect our four site and our three site together using AI GRP basically this is in a form of a LAN extension if you are following with the one technologies nowadays that the ISP is providing, there is technology that they have which is a LAN extension.

Basically what they do is you can assign an interface from a router to their switch and the same and another interface to the to your router and another site to their switch and they kind of put it in the same VLAN so this is what I am trying to achieve here. The other thing is we will run ebgp on all the routers, okay and Let's assume that the path between our four and our two has a redundancy link as well. So even though you want to reach our four it could go from the traffic may go from r two to r three and an r three to r four. But since we will be running AI GRP, which is a, which is the protocol with a lower administrative distance than our than the rip, the traffic can just pass through the pass through switch, pass through the switch and then to r four.

And that's what we will be doing with the BGP protocol that we will apply we can make sure that the path does take effect and it should go through from r two to r three in case there is a packet that needs to traverse the the local So let's start first by going into the switch and assign the VLAN into these two interfaces. And we will move on with this topology and we will sort of with this topology we are covering the broad spectrum of what we have talked about so far. One is the configuration of the routers step by step, including the IP interfaces, which I have been not providing you that in the last two lectures, because I wanted a topology that will basically sum up all those topics that we covered. And the other thing is introducing the rip and the eigrp and different autonomous systems within within these routers and apply those configuration to the routers plus ebgp configuration into the routers.

So, this topology basically sums up everything that we have been talking about. So hopefully you will be enjoying the, the steps that I will be showing you. So let me just bring up the switch console here. And let's start configuring this topology. So So the best, the best thing to do is basically start with this switch into face range. We said both those interfaces are part of VLAN one and we'll say no shut.

The. The other thing I like to apply is the spanning tree. So here we are done that test only thing that we need to apply in the configuration here for this switch. Now we will move on to our three and I will bring up the console. So I'm here in our threes console, the first thing that we will see is if there is any, any interfaces that are configured so nothing is configured here. So let's move on.

First thing we know that there's a loopback interface or interface loopback zero IP address. loopback interfaces are always up. The other interface that we will will configure is serial interface as one slash two and as one slash three. No shot. The IP address here that we are going to give to this interface here is 192 168 dot 23 dot two, just to remain consistent. No shot.

We'll come back to our three ones we are going to configure the other. Let's just do the point to point configuration first. So we will now go into our to and configure the interfaces. So let me bring up the console. Okay, so our tos console is up here. So let's configure first the loopback interfaces.

Interface lol zero IP And interface loopback one now one thing about the interface 01 slash two we can make it DC. So we'll introduce a clock rate here. And we'll put 64,000 IP address we do have another interface here. I believe that's all we need to do in our two for now for the pointer point configuration. And if I do show IP interface brief, I can see all the interfaces configured. And most of all of them are up here.

So now we will move to our four. And let me bring up the console for our floor and then we will move on to to configure the interfaces. Okay, I'm here in the console of our four let's configure first the loopback interfaces interface loopback zero IP address interface loopback one IP address Same thing here this router via DC router going to put the IP address here 192 168 dot 13 dot one no shot and there's another interface which is zero slash zero IP address to be 192 dot 168 dot One no shut show IP interface brief. And yes, we do have all the interfaces up here it's up and running. And now we will move on to the tasks. So the first task is complete here completed topology and assign the IP to all the interfaces we have completed that and it should look okay here.

Now we have to run the rip protocol on all the serial interfaces. So we will, we will go from r three and go down to r two and then r four. So let me bring up the interface. The console for r three. Okay, so I'm in our three here. So when says the rip protocol, it is It means rip version two router rip version two no two summary.

And then we do have two networks here that we will be advertising in the rip protocol on the rip database. So its network 192 dot 168 dot 13 dot zero network 192 168 dot 23 dot zero okay let's go to our to now. So basically in our tool we only have one serial interface so router rip version two no odd To summary and the network is 192 168 dot 23 dot zero. That's all. Now let's go to our four. So I have the console for four here.

So similarly, we will configure our for router rip, version two. There's one interface here in our four on 68 dot 13 dot zero and that's about it. Okay, so now we will move on to task number three. It says run between our four and our two interfaces. So just before we do that, I just want to bring up the routing table for our four. As you can see there's a rip protocol running, which is basically showing the route for 192 168 23 dot zero, which is basically the network that is that is outside of our two is showing, and you can see there's a full convergence and the traffic is via 192 168 dot 13 dot two, which is this interface here, as you can see, and it's true serial interface, one slash one, so that's good.

So that's that's the result of you know, applying rep on on our floor. And similarly in our two will be showing the same thing. It will learn all the networks from our for. Now let's go ahead and do this piece. So we will introduce AI GRP and we can give it any autonomous system, basically. So I know under the task I did not put the autonomous system but that's fine router eigrp we're going to choose hundred, just for simplicity and I'll say network.

So the first network I will basically advertise under eigrp will be will be the interface network which is 192 dot 168 dot 10 dot one And the other network would be basically network. So that's the interface network that we are advertising in AI GRP. I was thinking maybe I should advertise the, the loopback address which is 11 1111 dot zero dot zero dot zero. I believe that's all I need to do under you eigrp. Let's move into our two. Let's bring up part two.

Same thing here 192 dot 168 dot dot 10 dot zero dot two. The other network that I would like to advertise the two to two dot okay that looks good So if I do show IP route and as you can see, I can see the network which is one dot one dot one dot one dot one that's advertised and in our for, and here also if I do a show, show IP route. So over here, it's learning the Yeah, it's learning the the route through Fast Ethernet, zero slash 041 dot one dot one. Okay, so it just took a little time here to get this air gap network advertised to our four and it was basically my mistake. I didn't realize that the network that we have to advertise is basically not to two dot zero dot zero dot zero but actually the full network part which is the interface IP address with zero dot zero dot zero dot zero dot zero.

So that's the network that we would be advertising and that's how we got here. So this is a common mistake that that happens. So basically what I did is I went to router three eigrp hundred in r two I said no network two dot two dot zero dot zero dot zero because usually this is not really a network and then I put in the network and the statement which is for the for the interface of loopback one. So I think we achieved phase number three, or task number three. Now we will go into E BGP configuration on the routers. So let me bring first our three and then we'll move on.

Okay, so our three seconds So is is in front of us. So what we have to notice before applying BGP is you have to make a note of the autonomous system First of all, and and basically the the neighboring interface IP addresses, and put those IP addresses into their own autonomous system. So let's start doing that. So count T, and then router BGP, and our autonomous system and our three is 65513, as you notice, is the private autonomous system. And the first network we will advertise is the loopback address here, which is network 30 dot zero dot zero dot zero. And the other command is neighbor.

And we know it's 192 dot 168 dot 13 dot one and remote As remote as 65511 and then another neighboring device is our to 192 168 dot 23 dot one remote as 65512 that's all we have to do in our three Now we will move on to our to our the console here for our two and we'll start configuring it will enable BGP router BGP to talk autonomous system for r 265512. And we will advertise the loopback address 20 dot zero dot zero dot zero. And we'll say neighbor we know where there's one neighbor here 192 168 dot 23 dot two, and remote as 65513. Now let's go to our four. As you can see the neighbor adjacencies formed between r three and r two. Let's do the same in r four.

Or at the console here for our four. router BGP 65511 advertise the network 10 dot zero dot zero dot zero that's the loopback IP network address. And then the neighbor 192 168 dot 13 dot two remote as 65513. Perfect. So we have the basically we have the neighboring adjacency that is formed. So if I do show IP BGP, I can see there's a neighboring adjacency that's formed between between between the 10 network Under 30 network, which is our three.

That's great. And now if I bring up part two, and I do the same thing show, IP BGP, I can see there's a network that's formed between r two and r three. Okay, there's one thing I noticed like if I go to show IP BGP, I only see two networks, which is basically its neighboring 10 dot zero dot zero dot zero which is basically the loopback interface or IP network for our phones. And 30, which is its own, but I don't see the 20 to 20 network, which I actually advertised. So from our two so because our three has to basically be able to see all the updates from our two, as well as from our four, so I don't see that. And the reason the reason why I did that is because I wanted to show you if you do show running config and I do section BGP, if you see what I have explained earlier is that if the interface IP address does not match the network, exactly.

BGP will ignore it. And that's exactly what happened here. BGP actually ignored the network. So In order to fix this I have to go into interface loopback zero and say let me say no IP address. Basically we have a problem with the subnet mask not getting and as you can see now I can see the loopback network in BGP getting advertised. And the reason why it's getting advertised now is because the interface network matches the statements in the BGP.

And the other thing is, as I said, it's a path vector protocol. BGP is a path vector protocol. And that's why it's learning the path that the networks are coming from. So that's another example I'm wanting to cover here. So this is good news. Now.

Now if I do, basically trace route now that's perfect. And if arto does trace route it's actually missing one here. So we will let it finish but let me explain here. So as you can see when I was trying to trace from our for the network, to to to the to tu tu tu, tu tu tu, tu, tu tu it was going around directly through the interface 192 168 dot 10 dot two. That means it was trying to take the the fastest route to get into this interface so basically took the Ethernet F Zero slash zero interface to get to our to it, which is great because that's what we want it. But if I do trace route 20 dot 20 dot 20.

As you can see it's taking the, the longer route which is basically the rip route, which is from from here all the way to r three, sorry, all the way to r three and then r three to r two. So in order to fix that behavior, what We can do in BGP is we could apply a backdoor command. And that's what, that's the purpose of this lab. So let's do that. Okay, so what we will do here is we will go back to the, to the BGP configuration. So if I do show running config, and to Section BGP and we will add one more line here we'll say, router BGP 65511.

And I will say network 20 dot zero dot zero dot zero mass Back door now if you notice we are we are basically informing are for in order to reach the network in our two, we have to use the backdoor. So we are not really putting the route that is localized but, but the route is trying to reach. So that's good. Now let's do the same thing in our two. If I do an art to show running config, section BGP add one more line about BGP mask. Okay so I basically checked why it is still choosing grip to go to and why the traffic still going to words are three and then to its destination.

The only reason why it does that is because the BGP administrative distance is basically 200 whereas revenue As you know, if I do show IP route rep, as you can see it is basically 110. So that's the reason why it goes all the way from it chooses the, the path that is basically with less with lower administrative distance. And that makes sense, basically. But we can see all the networks are good ties and there's full convergence on this network. And from this, I am concluding that we have achieved our purpose where we basically our if you look at our final routing table, we have BGP, we have rip and we have the eigrp all in one topology. And they're all working in harmony and the traffic is very much converged all across the network.

I thank you very much. I hope you have enjoyed this topology and we will continue and we will cover another chapter. And please keep on keep on following me in this course and I hope you will gain a lot. Thank you