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neighbor remote-as 1

Specify which AS the peer belongs to. The peer-address must be reachable in the IGP. (both sides use default route at the same time not allowed (IOS) )

The neighbor command has 2 meanings:

  1. Allow Peer use this address ( to access my port 179, but does not specify which address of my side, only check the peer source address
  2. On my side use update-source address to access port 179 of the address ( behind the ‘neighbor’ key-word. Is it possible to establish a TCP session, will see the Peer allows my update source address to access it or not?

R1/R2 Both routers run RIPv2,network direct and lo0, and run iBGP between this 2 routers:

R1:neighbor remote-as 1

R2:neighbor remote-as 1

Both Sides do not write ‘update-source’, (neighbor x.x.x.x update-source lo0, means that the update source of this router is the lo0 interface, and the BGP packet is sent with the address of this interface as the source address.)

R1 ‘neighbor’ point to R2 direct-ip-address

R2 ‘neighbor’ point to R1 lo0

Here I ask some Questions, if you have interesting, you can answer them:

1.Can be established neighbor or not?

2.If established, which direct TCP session will be up

a.R1 —–> R2 session

b.R2 —–> R1 session

you can use ‘show tcp brief’ and see it, Port 179 is destination port, greater than 1024 port is source port, so you can know which is source

3.On which router add which command, can make TCP sessions in both directions possible to establish successfully

4.If both directions TCP session can be established successfully, which direction TCP session will establish finally


For any questions feel free to post comments or contact me!

By Lecturer:  James Tao 

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