ANS-C01 Question 136
Select 2Your company is running a hybrid network setup with a corporate data center connected to AWS using AWS Direct Connect. The on-premises routers are configured with a Border Gateway Protocol (BGP) session to an AWS Direct Connect Gateway. You are tasked with ensuring that all traffic destined for your corporate data center from AWS resources is routed through Direct Connect, while maintaining a backup path through your existing Site-to-Site VPN connection. How can this routing requirement be achieved?
- A
Advertise a more specific prefix for your on-premises network over the Direct Connect BGP session.
- B
Advertise a less specific prefix for your on-premises network over the Site-to-Site VPN BGP session.
- C
Configure static routes in AWS to prioritize Direct Connect over Site-to-Site VPN.
- D
Use BGP route weights to prefer Direct Connect routes over Site-to-Site VPN routes.
- E
Use AS_PATH prepending on the Site-to-Site VPN BGP session to make the path less preferred.
Show answer and explanation
Correct answers: A, E
Explanation
To ensure that AWS traffic destined for your on-premises network uses Direct Connect as the primary path, you can leverage BGP routing principles. Advertising more specific prefixes over the Direct Connect BGP session ensures that traffic takes the Direct Connect route. Additionally, using AS_PATH prepending on the VPN BGP session makes the VPN path less preferred, ensuring it acts as a backup. These steps align with BGP's path selection process and provide dynamic failover capabilities.
- A. Correct.
This is correct. BGP routing prefers the most specific route to a destination. Advertising a more specific prefix over Direct Connect ensures that traffic destined for your on-premises network takes the Direct Connect path.
- B. Incorrect.
This is incorrect. Advertising less specific prefixes will not ensure backup routing. It could lead to routing conflicts or unintended traffic flows.
- C. Incorrect.
This is incorrect. Although static routes could be used, BGP dynamically handles failover and is preferred in this scenario. Static routes do not scale well for hybrid environments.
- D. Incorrect.
This is incorrect. AWS does not support BGP weight as a routing decision criterion. Instead, other BGP attributes like AS_PATH can be used for route preference.
- E. Correct.
This is correct. AS_PATH prepending increases the path length for the VPN route, making it less preferred by BGP, thereby prioritizing Direct Connect.