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ANS-C01: AWS Direct Connect Optimizing BGP Configuration for Secondary Link Usage

Master the art of configuring BGP for AWS Direct Connect links! Learn how to prioritize af-south-1 as a secondary link using community tags and local preference values for efficient network routing.

Table of Contents

Question

A company has two AWS Direct Connect links. One Direct Connect link terminates in the us-east-1 Region, and the other Direct Connect link terminates in the af-south-1 Region. The company is using BGP to exchange routes with AWS.

How should a network engineer configure BGP to ensure that af-south-1 is used as a secondary link to AWS?

A.

On the Direct Connect link to us-east-1, configure BGP peering to use community tag 7224:7100
On the Direct Connect link to af-south-1, configure BGP peering to use community tag 7224:7300
On the Direct Connect BGP peer to us-east-1, set the local preference value to 200
On the Direct Connect BGP peer to af-south-1, set the local preference value to 50

B.

On the Direct Connect link to us-east-1, configure BGP peering to use community tag 7224:7300
On the Direct Connect link to af-south-1, configure BGP peering to use community tag 7224:7100
On the Direct Connect BGP peer to us-east-1, set the local preference value to 200
On the Direct Connect BGP peer to af-south-1, set the local preference value to 50

C.

On the Direct Connect link to us-east-1, configure BGP peering to use community tag 7224:7100
On the Direct Connect link to af-south-1, configure BGP peering to use community tag 7224:7300
On the Direct Connect BGP peer to us-east-1, set the local preference value to 50
On the Direct Connect BGP peer to af-south-1, set the local preference value to 200

D.

On the Direct Connect link to us-east-1, configure BGP peering to use community tag 7224:7300
On the Direct Connect link to af-south-1, configure BGP peering to use community tag 7224:7100
On the Direct Connect BGP peer to us-east-1, set the local preference value to 50
On the Direct Connect BGP peer to af-south-1, set the local preference value to 200

Answer

C.

On the Direct Connect link to us-east-1, configure BGP peering to use community tag 7224:7100
On the Direct Connect link to af-south-1, configure BGP peering to use community tag 7224:7300
On the Direct Connect BGP peer to us-east-1, set the local preference value to 50
On the Direct Connect BGP peer to af-south-1, set the local preference value to 200

Explanation

The correct configuration to ensure that af-south-1 is used as a secondary link to AWS is Option C. Here’s the breakdown:

  • For the Direct Connect link to us-east-1, the BGP peering is configured to use community tag 7224:7100.
  • For the Direct Connect link to af-south-1, the BGP peering is configured to use community tag 7224:7300.
  • The local preference value is adjusted: set to 50 for the Direct Connect BGP peer to us-east-1 and set to 200 for the Direct Connect BGP peer to af-south-1.

This setup ensures that af-south-1 is designated with a higher local preference value (200), making it more preferred over the us-east-1 connection, which has a lower local preference value (50). The community tags help distinguish the routes, allowing proper differentiation between the two Direct Connect links.

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