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RIP poison reverse benefit

Hi,

I've a question related to "poison-reverse" when used in conjuction with split-horizon (for instance in RIP protocol implementation)

Just to recap: split-horizon with poison reverse will advertise back with metric infinity (16 for RIP) a route out the interface from which it has been received with a metric of infinity (via a triggered/flash update).

Consider the following scenario:

R2-----serial--------R1---fast0/0 (10.10.1.1/24)

Suppose now R1 fa0/0 fail. R1 will remove the connected network (10.10.1.0/24) from IP routing table and, in turn, will send a triggered/flash update about 10.10.1.0 with metric 16 (inaccessible) to the serial i/f connected to R2. R2 following split-horizon w/ poison reverse rule will advertise back 10.10.1.0 with metric 16 to R1.

Now the question is: What is the purpose of the poison reverse route update from the point of view of the receiving router (R1 in the example) ? Which kind of action the receiving router (R1) will take upon the receiving of the poison-reverse route update ?

Thanks

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