Changing the route loop prevention method

Syntax:

no ip rip poison-reverse

Entering the command without the no option will re-enable Poison reverse.

RIP can use the following methods to prevent routing loops:

• Split horizon

  - the routing switch does not advertise a route on the same interface as the one on which the routing switch learned the route.

• Poison reverse

  - the routing switch assigns a cost of 16 (“infinity” or “unreachable”) to a route before advertising it on the same interface as the one on which the routing switch learned the route. This is the default.

These loop prevention methods are configurable on an individual VLAN interface basis.

Poison reverse is enabled by default. Disabling Poison reverse causes the routing switch to revert to Split horizon. (Poison reverse is an extension of Split horizon.) To disable Poison reverse on an interface, and thereby enable Split horizon, enter the following:

switch(config)# vlan 1

switch(vlan-1)# no ip rip poison-reverse