split horizon with poison reverse

Hey guys,

I am just going through RIP at the moment and doing some lab testing.
According to Doyle "RIP employs split horizon with poison reverse".

Take the following topology.

10.0.0.0/24 ---Router A ---192.168.0.0/24 ---RouterB----172.160.0/24

Split horizon is enabled on all interfaces. With this topology if split
horizon with poison reverse is the default then why do I not see the routers
sending back poisoned routes with debug ip rip? Is poison reverse an IOS
specific feature? I do note that split horizon is working in that routes
are not advertised out the interface they were received on.

RouterA

*Mar 1 00:05:00.731: RIP: sending v2 update to 224.0.0.9 via
FastEthernet0/0 (192.168.0.1)

*Mar 1 00:05:00.731: RIP: build update entries

*Mar 1 00:05:00.731: 10.0.0.0/24 via 0.0.0.0, metric 1, tag 0

*Mar 1 00:05:00.963: RIP: received v2 update from 192.168.0.2 on
FastEthernet0/0

*Mar 1 00:05:00.963: 172.16.0.0/24 via 0.0.0.0 in 1 hops

RouterB

*Mar 1 00:03:12.083: RIP: sending v2 update to 224.0.0.9 via
FastEthernet0/0 (192.168.0.2)

*Mar 1 00:03:12.083: RIP: build update entries

*Mar 1 00:03:12.083: 172.16.0.0/24 via 0.0.0.0, metric 1, tag 0

*Mar 1 00:03:14.791: RIP: received v2 update from 192.168.0.1 on
FastEthernet0/0

*Mar 1 00:03:14.791: 10.0.0.0/24 via 0.0.0.0 in 1 hops

/me scratches head.

Thanks,

-Aaron.

Blogs and organic groups at http://www.ccie.net
Received on Tue May 31 2011 - 15:54:24 ART