AWS Certified Advanced Networking – Specialty (ANS-C00) — Question 24

Your company has set up AWS Direct Connect to connect on-premises to an Amazon VPC instance. Two Direct Connect connections terminate at two different
Direct Connect locations. You are using two routers, R1 and R2, at your end (one of each Direct Connect connection). R1 and R2 do NOT have connectivity between them. Both routers advertise the same routers over BGP to the VGW. You have a stateful firewall on each router. The routers drop some of the traffic coming from the VPC.
Which two actions should you take to fix this problem? (Choose two.)

Answer options

• A. Use BGP AS prepend attribute to prepend additional AS numbers while advertising routers from R1 to VGW.
• B. Use BGP local preference attribute to assign R1 to a lower local preference number than R2.
• C. Use BGP local preference attribute to assign R1 a higher local preference number than R2.
• D. Use BGP MED attribute to assign a higher MED value to the routes advertised R1 to VGW.
• E. Use BGP MED attribute to assign a higher MED value to the routes advertised from R2 to VGW.

Correct answer: A, D

Explanation

Using BGP AS prepend on R1 helps influence the path preference towards that router by adding additional AS numbers, which can resolve routing issues. Additionally, applying a higher MED value on R1 helps prioritize that route over R2 when reaching the VGW. The other options either do not adequately address the routing preference or may incorrectly prioritize traffic away from the desired router.