Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Computing > Cisco > route poisoning and reverse poisoning

Thread Tools

route poisoning and reverse poisoning

Posts: n/a
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,


Reply With Quote
Posts: n/a

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

Reply With Quote
Posts: n/a
Ahh that clears up my confusion.

Thank you for your time Merv.

Reply With Quote

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Re: DNS Poisoning - advice/help sought +a Question Mike Easter Computer Support 9 11-20-2009 06:05 AM
What is the default precedence: local-route, static-route,OSPF-route? Cisco 9 08-07-2008 05:42 PM
ARP Poisoning? Steven B Cisco 5 07-16-2007 12:24 PM
Route poisoning ? jh3ang Cisco 1 04-07-2006 08:21 PM
DNS Poisoning and "Pharming" Michael Pelletier Computer Security 2 04-12-2005 05:36 AM