BGP requirements

Discussion in 'Cisco' started by Richard R. Field, Apr 8, 2004.

  1. Hi, my company is looking at beefing up our internet connection (currently a
    point to point T1 to an ISP) - replacing the ISDN backup with a T1 line to a
    second ISP. We would like to run BGP to make the redundancy work best. The
    new ISP requires that both internet subnets be at least /24 subnets, giving
    us a total of 508 public addresses (254 from each ISP). We currently have a
    /28 subnet (14 addresses). It's true that we could probably use more
    addresses since we are running out so I'm not complaining about getting a
    ton more addresses- Just wondering if this is a normal requirement, needing
    two full Class C subnets.

    Richard Field
     
    Richard R. Field, Apr 8, 2004
    #1
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  2. In article <ct3dc.94362$K91.213825@attbi_s02>,
    "Richard R. Field" <> wrote:

    > Hi, my company is looking at beefing up our internet connection (currently a
    > point to point T1 to an ISP) - replacing the ISDN backup with a T1 line to a
    > second ISP. We would like to run BGP to make the redundancy work best. The
    > new ISP requires that both internet subnets be at least /24 subnets, giving
    > us a total of 508 public addresses (254 from each ISP). We currently have a
    > /28 subnet (14 addresses). It's true that we could probably use more
    > addresses since we are running out so I'm not complaining about getting a
    > ton more addresses- Just wondering if this is a normal requirement, needing
    > two full Class C subnets.


    You should only need *one* /24 network, not two. You don't need a block
    from each ISP, just from one of them. You'll then advertise that one
    network through both ISPs to get failover.

    The reason you need a full /24 is because many ISPs will filter out BGP
    advertisements smaller than this. Any ISP that doesn't see the
    advertisement will not get the full benefit of the failover.

    --
    Barry Margolin,
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
     
    Barry Margolin, Apr 8, 2004
    #2
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  3. Richard R. Field

    theapplebee

    Joined:
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    Last edited: Sep 16, 2009
    theapplebee, Jul 25, 2009
    #3
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