300-410 Question 19
Single answerA network engineer is troubleshooting a routing issue in their OSPF network. A specific route is not being advertised to one of the neighboring routers, and upon investigation, the engineer observes that the route is being suppressed due to a loop prevention mechanism. Which mechanism is most likely causing this behavior?
- A
Split horizon
- B
Route tagging
- C
Route poisoning
- D
OSPF LSA Type 4 filtering
Show answer and explanation
Correct answer: A
Explanation
The split horizon rule prevents a router from advertising a route back out of the same interface on which it was received. This is a common issue when troubleshooting loop prevention mechanisms in OSPF or other routing protocols, as it directly impacts route advertisements. In this case, split horizon is the most likely cause of the suppressed route.
- A. Correct.
Split horizon is a loop prevention mechanism that prevents a router from advertising a route back out of the same interface on which it was learned. This is the most likely cause of the suppressed route advertisement in this scenario.
- B. Incorrect.
Route tagging is used for route identification and policy enforcement, not directly for loop prevention. This is not the likely cause here.
- C. Incorrect.
Route poisoning is a technique used in distance vector protocols to advertise a route with an infinite metric, making it unreachable. It is not directly applicable to this OSPF scenario.
- D. Incorrect.
OSPF LSA Type 4 filtering is used to control the advertisement of ASBR summary routes, but it is not a standard loop prevention mechanism and is unlikely to be the cause in this context.