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
    #1
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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
    #2
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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
    #3
  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.

    SysAdm
     
    itstime, Nov 12, 2006
    #4
  5. response3

    response3 Guest

    Got it. Thanks for the help!
     
    response3, Nov 14, 2006
    #5
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