glbp and bgp

Discussion in 'Cisco' started by D.Albertson, Oct 27, 2003.

  1. D.Albertson

    D.Albertson Guest

    Anyone have any expierience with GLBP (gateway load balancing proto 12.3
    ios) and multihomed bgp?


    Lets say for instance


    we have 2 ciscos each running bgp with a different upstream
    now would it be a bad idea to put GLBP in the mix with the intent
    of load balancing out bound traffic across wan links?

    Would there be an issue of potentially causing problems with packets
    arriving out of order
    at the recieving side do to a longer trip for half of the packets


    assuming we had one sprint link and one att link and we were sending packets
    to a sprint customer
    I guess all the packets sent through the sprint pipe would get there before
    the ones going through the att pipe.

    Maybe some kind of flow cache can be implemented?

    I guess I am just wondering if anyone is running a multihomed bgp setup and
    GLBP ?

    Thanks much!
     
    D.Albertson, Oct 27, 2003
    #1
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  2. Well, I'm using GLBP, but not with BGP, but it really doesn't matter.
    GLBP has the concept of an Active Virtual Gateway (AVG) and Active
    Virtual Forwarders (AVFs). The AVG assigns a virtual mac address to
    each member of the GLBP group (including itself). The AVFs are
    responsible for forwarding traffic for/responding to their assigned
    mac address. The other members of the GLBP group back each other up in
    case of failure.

    When a host arps for its default gateway (the virtual IP address in
    the GLBP group), the AVG responds with a virtual mac address for a
    router in the GLBP group. There are several ways to configure this
    distribution, check the docs. So, the question is, what is behind
    your two routers? A single firewall, a LAN with all your hosts? If a
    single firewall, then GLBP really won't do a lot for load distribution
    since the firewall will arp once and take that router until it needs
    to re-arp. Then it will get the virtual mac of the other router, then
    use that one. It's a little better than just using HSRP.

    If you have a LAN with all your hosts behind it (same subnet as the
    routers), then you'll get good load distribution across the ISPs. You
    most likely will have some asymetric routing, but you won't really
    have out-of-order packets, because each host is tied to sending data
    to a particular router, and in your case, one ISP.

    HTH,

    Mike

    "D.Albertson" <> wrote in message news:<>...
    > Anyone have any expierience with GLBP (gateway load balancing proto 12.3
    > ios) and multihomed bgp?
    >
    >
    > Lets say for instance
    >
    >
    > we have 2 ciscos each running bgp with a different upstream
    > now would it be a bad idea to put GLBP in the mix with the intent
    > of load balancing out bound traffic across wan links?
    >
    > Would there be an issue of potentially causing problems with packets
    > arriving out of order
    > at the recieving side do to a longer trip for half of the packets
    >
    >
    > assuming we had one sprint link and one att link and we were sending packets
    > to a sprint customer
    > I guess all the packets sent through the sprint pipe would get there before
    > the ones going through the att pipe.
    >
    > Maybe some kind of flow cache can be implemented?
    >
    > I guess I am just wondering if anyone is running a multihomed bgp setup and
    > GLBP ?
    >
    > Thanks much!
     
    Mike Gallagher, Oct 28, 2003
    #2
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