Sub dividing the block of IPs in different backbones

Discussion in 'Cisco' started by medamuralikrishna, Feb 24, 2006.

  1. Dear sir

    I am working for one of the leading ISP in INDIA.

    I am faceing Problem with one of my customers

    For this i want your help

    The problem is i have one class C IP Block Ex:

    This block is advertised in 2 ISPs with BGP

    I can advertise this block in any one of the Backbones.

    But I want to get the (Inbound) traffic of on one
    backbone , Remaing traffic on other backbone. How this can be passible
    in Core router.

    If you give the solution i am very thankful to you

    medamuralikrishna, Feb 24, 2006
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  2. cannot be a /28 -- it is at most a /29.

    I have not used BGP myself. What I have read about it suggests
    that what you want to do is possible in theory but not in practice,
    as the policy is usually not to advertise AS numbers with prefixes
    that long, so as to avoid filling up routing tables with lots of
    small entries.

    The usual solution to this would be to get a second IP range
    from the one ISP that the traffic is to travel on and to use that
    for the single-backbone traffic. That distinct IP range would
    be as large or as small as needed, since it would be part of
    the IP range allocated to that ISP and so that ISP would be
    aggregating the IP into a larger block for BGP advertising purposes.
    Walter Roberson, Feb 24, 2006
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