poison-reverse

Enables poison reverse loop prevention, either globally or on an individual interface, by assigning an "unreachable" cost to a route before advertising it on the interface where the route was learned. The global command can be used for RIP or RIPng routes.
Syntax
poison-reverse
ip rip poison-reverse
no poison-reverse
no ip rip poison-reverse
Command Default

By default, split horizon loop prevention is in effect. Split horizon does not advertise a route on the same interface as the one on which the device learned the route.

Modes

RIP router configuration mode, RIPng router configuration mode, or interface configuration mode

Usage Guidelines

The no form of the command disables poison reverse loop prevention.

Either poison reverse or split horizon loop prevention is always in effect on an interface enabled for RIP. When poison reverse is disabled, split horizon loop prevention is applied.

Examples

The following command enables poison reverse loop prevention for RIP on a device. 

device# configure terminal
device(config)# router rip
device(config-rip-router)# poison-reverse

The following example disables poison reverse and re-asserts split horizon loop prevention for RIP on the device. 

device# configure terminal
device(config)# router rip
device(config-rip-router)# no poison-reverse

The following example enables poison reverse for RIP routes on Ethernet interface 1/2/3. 

device# configure terminal
device(config)# interface ethernet 1/2/3
device(config-if-e10000-1/2/3)# ip rip poison-reverse

The following example enables poison reverse for RIPng on a device. 

device# configure terminal
device(config)# ipv6 router rip
device(config-ripng-router)# poison-reverse
Parent topic: Commands O, P, Q, R, and Sa through Sh