Which action does route poisoning take that serves as a loop-prevention method?
A. It immediately sends routing updates with an unreachable metric to all devices
B. It prohibits a router from advertising back onto the interface from which it was learned
C. It advertises a route with an unreachable metric back onto the interface from which it was learned
D. It poisons the route by tagging it uniquely within the network
correct answer is C.
A is correct
C describes Poison reverse , similar action but different function
Poison reverse – A variant of split-horizon whereby a router actively advertises routes as unreachable over the interface over which they were learned by setting the route metric to infinite (16 for RIP)
Route poising – When the protocol detects an invalid route, all of other routers in the network are informed that the bad route has an infinite (∞) route metric (16 for RIP)