300-420 Question 79
Select 3An enterprise network is running OSPF as its IGP. The network administrator wants to enable Graceful Restart to ensure minimal disruption during OSPF process restarts. Which of the following conditions must be met for Graceful Restart to function correctly in this OSPF network?
- A
The OSPF routers must support the Graceful Restart capability.
- B
The restarting router must maintain forwarding plane functionality during the restart.
- C
All OSPF neighbors must be configured in passive mode.
- D
OSPF neighbors must not detect a topology change during the restart.
- E
The OSPF process must be restarted manually by the administrator.
Show answer and explanation
Correct answers: A, B, D
Explanation
Graceful Restart in OSPF allows a router to restart its OSPF process without disrupting the network. This is achieved by maintaining the forwarding plane during the restart and coordinating with OSPF neighbors that support the feature. Additionally, the process is only considered 'graceful' if no topology changes are detected during the restart. These conditions ensure minimal disruption to traffic flow and routing stability.
- A. Correct.
This is correct. Graceful Restart requires that OSPF routers explicitly support the Graceful Restart capability. This ensures that neighbors can coordinate properly during the restart process.
- B. Correct.
This is correct. The restarting router must continue forwarding traffic during the restart to avoid packet loss, which is a critical component of Graceful Restart.
- C. Incorrect.
This is incorrect. Passive mode is not a requirement for Graceful Restart. Passive mode only prevents OSPF from forming adjacencies on certain interfaces.
- D. Correct.
This is correct. Graceful Restart assumes that no topology changes occur during the restart. If a topology change is detected, the process will not be considered 'graceful' and will fall back to a normal OSPF restart.
- E. Incorrect.
This is incorrect. Graceful Restart can be triggered automatically (e.g., during a software upgrade or process failure) and does not require manual intervention.