ANS-C01 · Question #219
A network engineer configures a second AWS Direct Connect connection to an existing network. The network engineer runs a test in the AWS Direct Connect Resiliency Toolkit on the connections. The…
The correct answer is C. Configure Bidirectional Forwarding Detection (BFD) on the on-premises router. A Direct Connect failover test shows a long interruption time (90 seconds), and the goal is to reduce this failover duration.
Question
A network engineer configures a second AWS Direct Connect connection to an existing network. The network engineer runs a test in the AWS Direct Connect Resiliency Toolkit on the connections. The test produces a failure. During the failover event, the network engineer observes a 90-second interruption before traffic shifts to the failover connection. Which solution will reduce the time for failover?
Options
- ADecrease the BGP hello timer to 5 seconds.
- BAdd a VPN connection to the connectivity solution. Implement fast failover.
- CConfigure Bidirectional Forwarding Detection (BFD) on the on-premises router.
- DDecrease the BGP hold-down timer to 5 seconds.
How the community answered
(31 responses)- A3% (1)
- B10% (3)
- C71% (22)
- D16% (5)
Why each option
A Direct Connect failover test shows a long interruption time (90 seconds), and the goal is to reduce this failover duration.
Decreasing the BGP hello timer to 5 seconds would shorten the interval at which hello messages are sent, but BGP's detection of a dead peer primarily relies on the hold-down timer. BFD provides much faster detection than even aggressive BGP timers.
Adding a VPN connection is a different connectivity solution altogether and implementing "fast failover" via VPN doesn't directly address reducing failover time for the *Direct Connect* connection specifically.
Bidirectional Forwarding Detection (BFD) is a protocol that rapidly detects communication failures between routing peers. When configured on the on-premises router for Direct Connect BGP sessions, BFD can detect a connectivity issue much faster than standard BGP timers alone, significantly reducing failover time for network paths.
Decreasing the BGP hold-down timer to 5 seconds would accelerate BGP's detection of a dead peer, but BFD can detect failures in milliseconds, making it significantly faster and more effective for rapid failover than tuning BGP timers alone.
Concept tested: Direct Connect fast failover with BFD
Source: https://docs.aws.amazon.com/directconnect/latest/UserGuide/resilience-toolkit.html
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