300-420 Question 95
Select 3A network design team is tasked with ensuring fast convergence within an enterprise network running OSPF. The team has been instructed to minimize downtime during link failures and optimize recovery time. Which of the following actions should they include in their design to achieve this goal?
- A
Enable Bidirectional Forwarding Detection (BFD) on all critical OSPF links.
- B
Reduce OSPF hello and dead timers on critical interfaces.
- C
Disable LSA throttling to accelerate link-state advertisement propagation.
- D
Use OSPF summarization at area boundaries.
- E
Enable OSPF fast reroute (OSPF FRR) for critical paths.
Show answer and explanation
Correct answers: A, B, E
Explanation
Fast convergence in OSPF can be achieved by implementing mechanisms that reduce failure detection and recovery times. Enabling BFD provides rapid failure detection, while reducing hello and dead timers ensures faster detection of link issues. Additionally, OSPF fast reroute (FRR) precomputes alternate paths to minimize downtime during failure events. These actions, when applied strategically on critical links, ensure optimal recovery time in enterprise networks.
- A. Correct.
Enabling Bidirectional Forwarding Detection (BFD) allows OSPF to detect link failures at sub-second intervals, significantly improving convergence times. This is a recommended practice for fast convergence.
- B. Correct.
Reducing OSPF hello and dead timers decreases the time it takes for OSPF to detect a link failure. This helps achieve faster convergence within the network.
- C. Incorrect.
Disabling LSA throttling is not recommended as it could lead to instability and excessive CPU utilization during convergence. LSA throttling is designed to control the rate of link-state advertisement propagation.
- D. Incorrect.
Using OSPF summarization is beneficial for scalability and stability, but it is not directly related to fast convergence. Summarization can delay convergence in some cases due to abstracted topology information.
- E. Correct.
Enabling OSPF fast reroute (FRR) allows traffic to be redirected immediately to precomputed alternate paths upon link failure, ensuring minimal downtime and faster convergence.