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From: vos on 13 Mar 2006 08:51
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

From: Merv on 13 Mar 2006 09:28

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

From: vos on 14 Mar 2006 01:28
Ahh that clears up my confusion.

Thank you for your time Merv. :)

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