Lesson 3: Configuring iBGP
In this free training video, Narbik Kocharians continues by configuring iBGP as step four in his process. He does this between the two PE routers. In router two, he establishes an iBGP peer session with router five's serial 1/4 interface. And then in router five, he establishes a peer session with router two's 1/3 interface.
Narbik takes a moment to consider what it would be like in a CCIE lab if the tasks stipulated that the two PE routers should only exchange VPN v4 routes. He then walks through the process to running that configuration.
Narbik notes that even though the peer session came up with the configuration, he will still have a problem. When router five uses the loopback interfaces, and the routers use their loopback interfaces to establish their peer session, there will be a healthy LSP from router two to router five. But if he uses the interface of router five, and the interface of router two, the LSP will be broken. If he sets the labels to be set to be based on the IP address of serial 1/4 interface, router four is going to assign a label of implicit null, or layer number three. And that will tell the pen ultimate hot popper router to pop the label on the way to router four. If router 3 pops the label, the LSP will be broken. So Narbik removes BGP and reconfigures it based on the loopbacks in order to fix the issue. This ends step number four.
The fifth step Narbik begins to implement is to configure VRFs. He does this by going to routers two and five to begin the process. Narbik notes that he sometimes sees people assign a huge name, but if if done that way, it must be repeated with every show command. So he recommends to use small, meaningful names in the lab. When Narbik configures the route target, it will be assigned to VPN v4. That means that he will have to go to address family VPN v4, and send extended communities to router five. As a good engineer, you should never rely on defaults, Narbik says.
Narbik then goes to his interface, facing router one, and the first thing he does is "do sh int 1/1." The minute he applies the VRF to serial 1/1 interface of router two, it will remove that IP Address. If you are in the lab, and that IP Address is removed, the proctor might not give it back to you. Narbik notices that in 15 code, it doesn't give you the IP Address.