Lab  8.6.1.2 EBGP- Multihop

Objectives:

  • To establish a BGP connection between routers via a router that is not running BGP.

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 your 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 192.16.2.1 255.255.255.0
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 
ip route 192.16.1.0 255.255.255.0 192.16.2.1
ip classless
RTC's configuration is:
ip subnet-zero
interface Serial1/1
ip address
192.16.2.2
255.255.255.0
 
router ospf 10
network 192.16.0.0 0.0.255.255
area 0
ip classless

The task to be completed in this lab is to configure a BGP connection between AS 1 and AS 2. The dilemma is that Router A is not capable of running BGP. To make this connection, you are going to have to use the ebgp-multihop command.

Configure Router B:

  1. Enable BGP on Router B using the router BGP 2 command.
  2. Synchronization is not needed here so turn it off with the no synchronization command. 3. It is now time to enter in the BGP neighbors. Since Router A is not running BGP, it cannot be our neighbor. So our neighbor will be the serial 0 interface of Router C. To assign Router C as our neighbor, issue the following command:
  3. RTB(config-router)# neighbor 192.16.2.2 remote-as 1

  4. So far we have done nothing new. The next thing we have to do is specify that we must go through 2 hops to get to Router C. To do this, use the command:
  5. RTB(config-router)# neighbor 192.16.2.2 ebgp-multihop 2

  6. Save your configuration and move on to Router C.

Configure Router C:

  1. You are on your own to figure out the commands to configure Router C. However, the tasks to be completed are to enable BGP and enter in the appropriate neighbor statements. Hint: You will need 2 neighbor statements. Use the steps for Router B as a guide.

Verification:

Verify you can reach Router B. This can be achieved by using the ping, trace, and viewing the routing table. Use the debug commands you have learned to view the negotiation and update process. Do you notice anything different?