Hello, this is your host Habib Korea and we are moving on to our next topics in BGP, but so far we have done tremendous progress in BGP, we have seen topologies that we covered BGP and ebgp adjacencies. And we established the relationships between ibgp routers and the same autonomous systems, and external BGP, using different autonomous systems. We have covered the topic of BGP in configuration. And we also covered BGP and route reflector, and how we mitigate it through to resolving the issues that are caused by split horizon rule. And also we have covered the topology that we introduced. used which is a BGP backdoor and we also have done BGP advertisement using loopback addresses and how we use it to basically utilize or have fault tolerance for links that are basically redundant.

So these are very important topics we covered in BGP. And this topic, chapter seven is basically also as important as the previous lessons. And basically in this topology as it is shown, the customer has its own autonomous system. And it's running a s 6551 to the customer will be basically advertising its loopback address 20 2020 dot 20 slash eight, or basically 20 dot zero dot zero dot zero slash eight network to the ISP. The ISP has basically one connection to the customer as you can see, and the ISP has basically another router within its domain and it wants to make sure that the network that's coming from the customer is also converged in our three. So basically the tasks are number one, complete the topology and assign the IP to all the interfaces as you can see, and then we will run ebgp on ISP one and the customer router and we will make sure that the customer should advertise the loopback address which is 20 dot zero dot zero dot zero slash eight.

We will also run an ibgp between the ISP router and the router But we will investigate why this network is not showing in our three, and what will could be the reason and we will apply effects. So I hope you'll join me. I will pause for basically a few minutes and I will come back. And I will complete basically the first task which is assigning the IP address to all the interfaces. And we will start with task number two. The first task is simple.

We went through it many times in our previous lessons. Basically, it's about assigning IP addresses to the interfaces. That is really very simple to do. So, hang on in there. Let me come back with the routers up and running with the interfaces configured. Okay, so I'm back and I've configured the customer router and I've basically Putting the the IP address on the interfaces as you can see so far Fast Ethernet one slash zero spacing is p one and I've given it 192 168 dot 10 dot one and it's slash 22.

Now, slash 24 network for introduced the loopback address as you can see, and similarly I have also configured the, the ISP one router, as you can see, and I have configured the router three as well. router three with the with the IP show IP interface brief. And you can see I have the interfaces. Now there's nothing in the routing table show IP route. So it's only the static and the connected local IP addresses that are Already there the networks that are there already. So that's good.

So the first thing we will do now is basically form the BGP relationship right? So with so let's start with the customers router first. So called t router BGP. And then we say it has the autonomous system here is going to be 65512. And now also what we need to do is put the neighbor Rainie where IP addresses 192 168 dot 10 dot two I believe, and we will basically to remote as and the autonomous system of ISP is 65511 Ok, and now we will also want to advertise the network which is 20 dot zero dot zero dot zero. And the mask is 255 dot zero dot zero.

Right. So that's all we need to do at the customer site right now. Okay, now let me bring up ISP one. let's configure that router BGP 65511 right. And we will do the neighboring information. So neighbor First neighbor is 192 dot 168 dot 10 dot one remote as 65512.

That's because tomorrow is number. And then we also have another neighbor 10 dot 10 dot 10 dot two remote as 65511. Now let's bring up the router three and let's talk a configuration in law To three which is to BGP 65511. We have a neighbor TASS 655. We can see ibgp relationship established between r three and ISP one. Now if you look closely now let's let's investigate a little bit.

So if I do on ISP one, I do show IP BGP I can see the network 22 dot zero dot zero. And the next hop is 192 168 dot 10 dot one, right. And if I do show IP route, show IP route, I can see BGP route is available here in the IP route. That means the router injected the BGP route into its routing table. Which is good. Now if I look at this r three, and I do show IP, BGP.

Now you can see that 20 dot zero dot zero dot zero is being advertised to our three, but the next hop is 192 168 dot 10 dot one than that Hall 10 dot one, which is this one, right? That's 10 dot one. But there's no relationship between our three and the customer. Customer interface, right? The reason why that happened is because the ISP is advertising the route to our three. But it's also passing on the information to our tree that that network is getting advertised from that interface over there from the customers network.

Right. But if I do on our three, if I do show IP route, I don't see the 20 network and the IP route here because the reason is, it's not allowing BGP is not allowing the network 20 dot zero dot zero than zero to be converting are three because it doesn't see 192 168 dot 10 dot one as its next hop in order to fix this issue. What the ice peas do is they basically come to ISP one, right? And what they will do is basically introduce is p one and adjust that route, right. So if I go if I do an ISP one show running config, and I do section BGP, I want to see what's in the BGP here. So you can see the neighbor which is 10 dot 10 dot 10 dot two remote as 655 656-565-5655 One one and then the neighbor is 192 168 dot 10 dot one remote as 65512.

Right. So let me fix that. What I'll do is I'll go into the BGP router configuration 65511. And I'll say neighbor 10 dot 10 dot 10 dot two. Next up so basically I will clear IP, BGP asterik analysis and there you go. I can see in the routing table I can see 20 dot 20 dot 28 network and it's getting advertised via 10 dot 10 dot 10 dot one.

So this is the purpose of, of basically next hop self. I hope it's clear now, how it's working. And why it is important important is now our three which already has a relationship with the ISP router can actually see the see the network 20 dot zero dot zero dot zero slash eight That's great. If I do show IP BGP summary, though, I do show IP route. I can see the routers, the the network is there and it's getting advertised. That's perfect.

And that was the purpose of the lab and we actually have fixed all the six tasks that was given to us to complete. And see you see you again in my next topic. Thank you.