300-420 Question 96
Single answerA network engineer is designing a large enterprise network that must support fast convergence and avoid loops in case of link or node failures. The network will primarily use Layer 3 routing protocols. Which technology or feature should the engineer implement to achieve a loop-free topology with the fastest failover times?
- A
Fast Reroute (FRR) using Loop-Free Alternate (LFA)
- B
Spanning Tree Protocol (STP)
- C
Equal-Cost Multi-Path (ECMP)
- D
Virtual Router Redundancy Protocol (VRRP)
Show answer and explanation
Correct answer: A
Explanation
Fast Reroute (FRR) with Loop-Free Alternate (LFA) is designed to ensure fast failover and loop-free forwarding in Layer 3 environments by precomputing backup paths. It is a modern and efficient solution for achieving the requirements stated in the scenario, making it the most suitable choice. Other options like STP and VRRP either operate at a different layer or do not address the specific requirements of fast convergence and loop-free design.
- A. Correct.
Fast Reroute (FRR) using Loop-Free Alternate (LFA) is a mechanism used in modern Layer 3 routing protocols (like OSPF and IS-IS) to precompute backup paths for fast failover and loop-free forwarding. This is the best option for achieving a loop-free topology with fast convergence in a Layer 3 network.
- B. Incorrect.
Spanning Tree Protocol (STP) is a Layer 2 protocol designed to prevent loops in Ethernet networks. While it avoids loops, it has slower convergence times compared to Layer 3 solutions and is not ideal for the scenario described.
- C. Incorrect.
Equal-Cost Multi-Path (ECMP) allows for load balancing across multiple paths of equal cost. While it improves performance, it does not inherently provide a loop-free mechanism or fast failover like FRR.
- D. Incorrect.
Virtual Router Redundancy Protocol (VRRP) provides redundancy for gateway routers in Layer 3 networks but does not offer a solution for loop-free topology or fast convergence during link or node failures.