Changing the route loop prevention method
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.
NOTE:
These methods are in addition to RIP's maximum valid route cost of 15.