Lab 8.6.1.1 Building Peering Sessions : IBGP vs. EBGP

Objective: 

To establish a basic BGP connection between routers and observe differences between internal and external BGP sessions.

Before focusing on the BGP portion of the lab, complete the following steps:

  1. Setup the lab as shown in the diagram. 
  2. Assign IP addresses to each interface as shown in the diagram. The L0 address represents a loopback address. Make sure you set up these as well. 
  3. Enable OSPF as the routing protocol between Router A and Router B. 
  4. Advertise network 192.16.1.0 with a wildcard mask of 0.0.255.255.

Verify you configurations are as follows:

RTA's configuration is:

ip subnet-zero
interface Loopback0 
ip address 192.16.3.1 
255.255.255.0
interface Ethernet0
ip address 192.16.1.1 
255.255.255.0
interface Serial1 
ip address 192.16.2.1
255.255.255.0
router ospf 10 
network 192.16.1.0 0.0.255.255 
area 0
ip classless

RTB's configuration is: 

ip subnet-zero
interface Loopback0
ip address 192.16.4.1
255.255.255.0
interface Ethernet1/1 
ip address 192.16.1.2
255.255.255.0
router ospf 10 
network 192.16.0.0 0.0.255.255
area 0 
ip classless

RTC's configuration is:

ip subnet-zero
interface Serial1/1
ip address 192.16.2.2 
255.255.255.0
ip classless

Now that we have the IGP set up, we can configure the BGP connections:

Begin with Router A:

  1. Enter global configuration mode.
  2. Enable BGP on router A for AS #2. To do this use the command:

RTA(config)#router bgp 2 RTA(config-router)#

  1. Since AS #2 is a small Autonomous system that is fully meshed and is not a transit AS, it is safe to turn off the synchronization feature of BGP. To do this issue the command:

RTA(config-router)#no synchronization

  1. Next we must define the BGP neighbor relationships. Router A has 2 BGP neighbors, namely Router B and C. To define these relationships issue the following commands:

RTA(config-router)#neighbor 192.16.4.1 remote-as 2  **Note the loopback address** 
RTA(config-router)#neighbor 192.16.4.1 update-source Loopback 0 
RTA(config-router)#neighbor 192.16.2.2 remote-as 1

Note the update-source Loopback 0 statement. This command specifies the interface to be used as the source ip address of the BGP session with the neighbor.

  1. Lastly, we are not going to summarize routes in this lab. So we will turn off the BGP automatic summarization at the major net boundary. To do this issue the following command:

RTA(config-router)#no auto-summary

  1. Save your configuration and move to Router B.

Configuring Router B:

  1. Before enabling BGP on this router, issue the following command:

RTB#debug ip bgp

This command will allow you to see the negotiation between BGP neighbors.

  1. Enable BGP on router B for AS #2.

What command will you need to do this? (HINT: See step 1 from Router A)

  1. Define the BGP neighbor relationships for router B.

What command(s) should you use to do this? 

  1. Shut down your Ethernet interface and then bring it back up again. You should now see the neighbor negotiation process on your screen.

List the steps of the negotiation process:

Issue the show ip bgp neighbor command.

What kind of BGP connection is this, internal or external?

How do you know what kind it is?

  1. Save your configuration and move to router C.

Configuring Router C:

  1. Enable bgp routing on Router C for AS #1.

What command will you need to do this?

  1. Define the BGP neighbor relationships for router C.

What command will you use to do this?

  1. Issue the show ip bgp neighbor command.

What kind of BGP connection is this, internal or external?

How do you know what kind it is?

  1. Verify connectivity with the ping command.

What addresses can you successfully ping?

What addresses can you not ping? 

Save your configuration.