iBGP - physical connection needed between peers?

Hi, I'm hoping someone can help with this. I have two edge routers (A,
B) running eBGP to two separate peers (1, 2) within my colo facility.
I have a single Catalyst 4500 w/ dual Sup II's, acting as my core
switch, which is connected to routers A, B. I am running EIGRP in my
LAN, and I am redistributing the default gateways into EIGRP. My
question is in order to run iBGP between my edge routers, do I need a
direct physical connection between them, or can my colo provider
somehow do multi-hop iBGP for me between them?

 

iBGP doesn't require a direct connection between peers, it supports
multi-hop automatically. This is because the default configuration of
iBGP is a full mesh of all the routers in the AS, but there's no
expectation that there will be a physical full mesh.

 

Thanks for the reply. I've heard about issues with syncronization
problems between iBGP and eBGP, which suggest there may be issues using
multi-hop iBGP. Are you aware of any such problems?

 

ibgp does not change the next hop address (to get it to, you will need to
use the neighbor x.x.x.x next-hop-self command)
ibgp will not advertise ibgp learnt routes to ibgp neighbours (unless you do
something fancy like route-reflect).

i think what you are getting at is the issue of turning sync off and having
a non-bgp speaker in the path -- that router will need to know (via IGP) how
to get to the ibgp-learnt prefixes.

SysAdm

 

Got it. Thanks for the help!