route poisoning and reverse poisoning

Discussion in 'Cisco' started by vos, Mar 13, 2006.

  1. vos

    vos Guest

    Hi all,

    I am studying for my ccna and due for my exam in a few weeks. I am a
    bit confused about the difference, if any, between route poisoning and
    reverse poisoning and was wondering if someone could explain the
    difference please? I have searched the matter but still carry confusion
    after reading differing explainations.
    Thank you,

    Regards,
    Vos
     
    vos, Mar 13, 2006
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  2. vos

    Merv Guest

    route poisoning and reverse poisoning are routing loop prevention
    techniques used by distance vector routing protocols.

    "Poison reverse allows routers to break the split horizon rule by
    advertising information learned from an interface out the same
    interface. However, it can advertise routes learned from an interface
    out the same interface with a 16 hop count, which indicates a
    destination unreachable, "poisoning" the route. Routers with a route
    with a better metric (hop count) to the network ignore the destination
    unreachable update."

    route poisoning is setting a route's metric to infinity (i.e. max hops
    + 1)

    poison reverse is the process of breaking the split horizon rule and
    sending a poisoned route back over the same interface from which it was
    learned
     
    Merv, Mar 13, 2006
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  3. vos

    vos Guest

    Ahh that clears up my confusion.

    Thank you for your time Merv. :)
     
    vos, Mar 14, 2006
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