300-420 Question 92
Select 3An enterprise network is running OSPF as its routing protocol. The network design team has been tasked with improving the network's convergence time in the event of a link failure. Which of the following design considerations would help achieve fast convergence in this scenario?
- A
Implement OSPF Bidirectional Forwarding Detection (BFD) for faster failure detection.
- B
Reduce the OSPF Hello and Dead intervals on all interfaces.
- C
Enable OSPF Graceful Restart to minimize disruptions during failure events.
- D
Optimize OSPF timers by configuring a lower SPF throttle timer.
- E
Increase the OSPF cost on high-bandwidth links to prioritize lower-cost paths.
Show answer and explanation
Correct answers: A, B, D
Explanation
Fast convergence in OSPF can be achieved by reducing the time taken to detect failures and propagate routing updates. Techniques like implementing BFD, optimizing Hello and Dead intervals, and reducing SPF throttle timers directly address these needs. Graceful Restart and cost adjustments, while useful in certain scenarios, do not directly improve convergence time during link failures.
- A. Correct.
Implementing OSPF BFD allows the network to detect link failures quickly, as BFD provides sub-second failure detection. This directly contributes to fast convergence.
- B. Correct.
Reducing the OSPF Hello and Dead intervals enables faster detection of neighbor state changes, helping to identify failures more quickly.
- C. Incorrect.
While OSPF Graceful Restart minimizes disruptions during events like router reboots, it does not directly improve convergence time during link failures.
- D. Correct.
Lowering the SPF throttle timer reduces the delay between SPF calculations, ensuring faster routing updates after a topology change.
- E. Incorrect.
Increasing the OSPF cost on high-bandwidth links does not contribute to faster convergence. Instead, it alters path selection, which is unrelated to convergence speed.