BGP Easy-multihome 

UPDATED: August 27, 1999

This Technote is meant to be an example NOT a complete BGP (Border Gateway Protocol) routing configuration.

Router Diagram

--------------------------
         +------------+  |        |  +------------+
  AS     |Router 1    |  |        |  |Router 2    | AS
 9966    |172.16.96.76|  |        |  |10.200.10.3 | 8855
         +------------+  |        |  +------------+
                   /     |        |     /
--------------------------        -----------------------
                 /                    /
           EBGP /               EBGP /
               /                    /
---------------------------------------------------------
              /      AS 9009      /
+------------+               +-------------+
|Router 3    |     IBGP      |Router 4     |
|192.168.10.5|---------------|192.168.10.3 |
+------------+               +-------------+
      |                                 |
      | IBGP            |---------------|
      |                 |      IBGP
+------------+          |            
|Router 5    |----------|
|192.168.10.6|          
+------------+          
  1. On all routers that are going to run BGP, make sure they have at least 16 MB of memory. To enable BGP, issue the following commands:


    2. set bgp enable
    save all
    reboot
     

  2. Our AS for this example will be 9009 . Issue the following command on all BGP routers:


    3. | set bgp id <IP number of ether0>
    set bgp as 9009
    save all
    reset bgp
     

  3. Setup the EXTERNAL peering to the two different providers.

  4. (Router 192.168.10.5 will receive it's feed from 172.16.96.76 AS 9966 and router 192.168.10.3 will receive it's feed from 10.200.10.3 AS 8855). 

    Set up the peers to these routers with the following commands: 

    On 192.168.10.3:
    add bgp peer 192.168.10.3 10.200.10.3 8855 easy-multihome
    save all

    On 192.168.10.5:
    add bgp peer 192.168.10.5 172.16.96.76 9966 easy-multihome
    save all
     

  5. Setup the INTERNAL peering to the AS 9009 router 192.168.10.6 . We will set each router to always be the next hop in the BGP path. Also setup the INTERNAL peering between 192.168.10.3 and 192.168.10.5 .


    6. On 192.168.10.3:
    add bgp peer 192.168.10.3 192.168.10.6 9009 accept all inject all advertise all always
    add bgp peer 192.168.10.3 192.168.10.5 9009 accept all inject all advertise all
    save all

    On 192.168.10.5:
    add bgp peer 192.168.10.5 192.168.10.6 9009 accept all inject all advertise all always 
    add bgp peer 192.168.10.5 192.168.10.3 9009 accept all inject all advertise all
    save all
     

  6. Setup the INTERNAL peering to the AS 9009 routers 192.168.10.3 and 192.168.10.5 routers from 192.168.10.6 . 


    7. On 192.168.10.6:
    add bgp peer 192.168.10.6 192.168.10.3 9009 accept all inject all advertise all

    add bgp peer 192.168.10.6 192.168.10.5 9009 accept all inject all advertise all

  7. Add summarizations for internal routes that you want to advertise to your providers.


    8. On 192.168.10.5:
    add bgp summarization 192.168.10.0/24 as 9966
    add bgp summarization 192.168.20.0/24 as 9966

    On 192.168.10.3:
    add bgp summ 192.168.10.0/24 as 8855
    add bgp summarization 192.168.20.0/24 as 8855