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Q4. Which of the following are possible solutions to prevent routing loops? [Choose all that apply].
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A. Split Horizon B. Poison Reverse C. Hold-down Timers D. Triggered Updates
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Correct answer: E
Explanation:
All the following are possible solutions for preventing routing loops.
1. Split Horizon - based on the principle that it is not useful to send the information about a route back in the direction from which the information originally came.
2. Poison Reverse - A router that discovers an inaccessible route sets a table entry consistent state (infinite metric) while the network converges.
3. Hold-down Timers - Holddown timers prevent regular update messages from reinstating a route that has gone bad. Here, if a route fails, the router waits a certain amount of time before accepting any other routing information about that route.
4. Triggered Updates - Normally, new routing tables are sent to neighboring routers at regular intervals (IP RIP every 30 sec / and IPX RIP every 60 sec). A triggered update is an update sent immediately in response to some change in the routing table. Triggered updates along with Hold-down timers can be used effectively to counter routing loops.
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