From: Nauman Khan (mustafa@247emails.com)
Date: Sat Jan 24 2004 - 06:49:39 GMT-3
Hi Alsontra,
Check out UniverCD BGP Command Reference for ebgp-multihop
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fiprrp_r/bgp_r/1rfbgp1.htm#1019394
and yes you would use it when establishing EBGP session with the peer
who is on a network which is not directly connected.
>--- <alsontra@hotmail.com> wrote:
>If your using loopback to source BGP sessions in a single direction, do >you have to specify "neighbor/ebgp-multihop " on both bgp peers?
>For example:
>(assuming that IGPs or statics are in place and life is good)
>(Lo1-1.1.1)--R1-------------R2
>R1 neighbors statements:
>neighbor 4.4.4.4 remote-as (100)
>R2 neighbor statements
>neighbor 1.1.1.1 remote-as 200
>neighbor 1.1.1.1 update-source-loopback Lo0
>neighbor 1.1.1.1 ebgp-multihop 255
Also, Looking at this config, it looks to me that on R2 you are saying R2 will be using lo0 (R2 lo0) to source bgp tcp connection to nighbor 1.1.1.1. So you must you use R2 lo0 when forming ebgp peering on R1 with R2. In your config , this makes 4.4.4.4 as R2 lo0.
Hence in this case, it looks to me that both R1 and R2 are using their loopbacks to form ebgp peering. Hence i would put
neigbor x.x.x.x ebgp-multihop 2
on both R1 and R2, where x.x.x.x is the loopback of the neighbor I am using to form peering.
Univer CD ref for update-source
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fiprrp_r/bgp_r/1rfbgp2.htm#1168071
Best Regards,
Nauman
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