Which technique is used to stop routing loops by preventing route update information from being sent back over
the interface on which it arrived?

A.
Holddown timer

B.
Triggered updates

C.
Route poisoning

D.
Split horizon

E.
Maximum hop count

Explanation:
Split horizon stops routing loops by preventing route update information from being sent back over the interface
on which it arrived. Routing loops can occur due to slow convergence and inconsistent routing tables, and can
cause excessive use of bandwidth or even complete network failure. Split horizon can prevent routing loops
between adjacent routers.
Holddown timers prevent regular update messages from reinstating a route that is unstable. The holddown
timer places the route in a suspended, or “possibly down” state in the routing table, and regular update
messages regarding this route will be ignored until the timer expires.
Triggered updates are sent as soon as a change in network topology is discovered, as opposed to waiting until
the next regular update interval (every 30 seconds in RIP networks). This speeds convergence and helps
prevent problems caused by outdated information.
Route poisoning “poisons” a failed route by increasing its cost to infinity (16 hops, if using RIP). Route poisoning
is combined with triggered updates to ensure fast convergence in the event of a network change.
Objective:
Routing Fundamentals
Sub-Objective:
Compare and contrast distance vector and link-state routing protocols

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