multihoming - 2 ISP/2 sites (no inbound traffic during failover)

Discussion in 'Cisco' started by joebenz, Mar 1, 2011.

  1. joebenz

    joebenz Guest

    We currently have 2 sites where an Internet POP is located. Both are
    doing eBGP and EIGRP and have ASAs behind them. One site is a library
    and the other is city hall. Currently city hall is advertising a /24
    associated with the site and the library advertises their own /28 and
    city hall's /24. City hall uses their internet connection as primary
    and library's as backup. Library uses theirs as primary and City
    hall's as backup. Right now, if either ISP fails, outbound traffic
    failsover to backup and there is no issue with users getting out to
    the internet. However, when city hall failsover to the library's ISP,
    even though the libary is advertising city hall's network, no traffic
    is getting in. We have the NAT and ACL configured for a city hall web
    server on the library's ASA, but it's still unreachable. Would you
    have any suggestions on why this would not be working? I can provide
    more information if needed.

    Thank you.
    joebenz, Mar 1, 2011
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  2. Most likely your provider won't pass or even accept /24 and for sure
    won't accept /28 advertisements because they are too small.

    To check this, when your primary connection is down, go to a BGP looking
    glass (like and take a look how your prefix
    is being advertised.

    Anonymous coward, Mar 19, 2011
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