iBGP - physical connection needed between peers?

Discussion in 'Cisco' started by response3, Nov 11, 2006.

  1. response3

    response3 Guest

    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?
    response3, Nov 11, 2006
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  2. 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.
    Barry Margolin, Nov 12, 2006
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  3. response3

    response3 Guest

    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?
    response3, Nov 12, 2006
  4. response3

    itstime Guest

    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.

    itstime, Nov 12, 2006
  5. response3

    response3 Guest

    Got it. Thanks for the help!
    response3, Nov 14, 2006
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