Least cost routing (BGP) between multiple carriers over MPLS internal network

Discussion in 'Cisco' started by Burt Gummer, Feb 8, 2006.

  1. Burt Gummer

    Burt Gummer Guest

    Currently we have a Frame network of six routers with two different ISPs,
    each at a different site. We have an ASN and three of our internal
    routers share BGP tables from the two providers. The remaining three
    routers are spokes to this core.

    The "core" is arranged in a triangle of Frame PVCS. So, we have an ISP
    coming in two two different legs (AT&T on one, Sprint on the other) and
    the three core routers share the BGP tables.

    We've being sold a MPLS solution.

    Our six routers will now be arranged as a full mesh. We're
    keeping the two ISPs. Currently we use the ISPs as fail-over and Least
    Cost Routing. Out MPLS vendor says the Label-to-route mapping is actually
    in the PE and full Internet BGP routing information is too much for them.

    My understanding of MPLS is limited, so I'm doing a fair amount of
    reading. I understand, I think, there are mechanisms where the mapping can
    be moved to the CE, thereby proving us with least cost routing across the
    full mesh because the mapping burden is in our routers. The PE, then,
    simply has a table of labels and routes based on those labels we
    (somehow) attach. Is any of this true?

    If my understanding s anywhere near correct, please point me to some
    reference material. My overall impression is my MPLS vendor is trying to
    screw me by removing functionality from my current network (LCR) and
    inserting themselves as a "managed" solution, with associative increased
    Burt Gummer, Feb 8, 2006
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  2. Burt Gummer

    Charlie Root Guest

    Do you really need full BGP? Normally prefixes of the direct ISP and his
    customers + default (possible conditionally set by you based on presence of
    certain prefix) should be enough, unless you're really into selecting which
    sites you want to reach via one ISP and which via another. It's quite common
    for PE routers to have only limited routing table (usually only prefixes
    within providers own network) as they reach all destination via one or two
    upstream routers. One of the possible solutions for you (if your providers
    have such option) is to use multi-hop eBGP towards one of the providers
    router that carries full-table.
    Although you indeed could do mapping on your CE, no provider will agree up
    on this due to security reasons (they don't want you to mess up service that
    they provide). In Frame Relay world it would be comparable if you'd try to
    get NNI connectivity with your ISP.
    Managed solution assumes they'd also manage your CE. It's very common among
    MPLS VPN providers. Actually it simplifies troubleshooting as there's no
    ping-pong arguing whos side is at fault. ISP doesn't want to screw you, but
    they might have not understood what exactly you want to achieve. Try to talk
    to them and explain why do you want to have full routing and see what they
    have to offer. Also try first to explain the problem to a manager in your
    company, so that he/she can escalate the problem with your providers more

    Charlie Root, Feb 10, 2006
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