300-420 Question 78
Single answerA network engineer is designing an enterprise network with redundancy in mind. They are using OSPF as the routing protocol and want to ensure minimal disruption when a router undergoes a planned restart. Which of the following is true about Graceful Restart in OSPF, and how it can help achieve this goal?
- A
Graceful Restart allows the restarting router to maintain its role as the Designated Router (DR) if it was previously elected as one.
- B
Graceful Restart ensures that neighboring routers never detect the restarting router as being down by suppressing LSA updates.
- C
Graceful Restart enables the restarting router to continue forwarding traffic while it re-establishes control plane functions.
- D
Graceful Restart works with all routing protocols, including RIP and EIGRP, without requiring additional configurations.
Show answer and explanation
Correct answer: C
Explanation
Graceful Restart in OSPF is a mechanism that allows a router to restart its control plane without interrupting its forwarding plane, minimizing traffic disruptions during planned restarts. To achieve this, neighboring routers must support the 'helper' mode and maintain the routing information temporarily. This ensures that traffic continues to flow while the restarting router re-establishes its OSPF adjacencies.
- A. Incorrect.
This is incorrect because Graceful Restart in OSPF does not guarantee that the restarting router will maintain its DR role. DR roles are re-evaluated during the neighbor establishment process.
- B. Incorrect.
This is incorrect because Graceful Restart does not suppress LSA updates indefinitely. Instead, it relies on neighboring routers supporting the 'helper' mode to temporarily avoid purging routes.
- C. Correct.
This is correct. Graceful Restart allows the router to continue forwarding traffic using the previously established forwarding plane while the control plane is restarted.
- D. Incorrect.
This is incorrect because Graceful Restart is protocol-specific and requires both the restarting router and its neighbors to support and be configured for the feature. It is not universally applicable to all routing protocols.