QuestionQ128

Network Design

A company operates in the us-east-1 Region and the us-west-1 Region. The company is designing a solution to connect an on-premises data center to its AWS environment in us-east-1. The solution uses two AWS Direct Connect connections.

Traffic from us-west-1 to the data center must traverse the Direct Connect connections. A network engineer needs to configure active-passive functionality across the two Direct Connect connections by using a Direct Connect gateway to influence inbound traffic from VPCs in us-west-1 to the data center.

Which solution meets these requirements?

  • A At the data center, set the local preference for the primary connection to be higher than the local preference for the secondary connection.
  • B Use AS path prepending to set the AS path on the primary connection to be longer than the AS path on the secondary connection.
  • C Use local preference BGP community tags to apply the 7224:7300 local preference BGP community tag to the prefixes for the primary connection. Apply the 7224:7100 local preference BGP community tag to the prefixes for the secondary connection.
  • D Use local preference BGP community tags to apply the 7224:9300 local preference BGP community tag to the prefixes for the primary connection. Apply the 7224:9100 local preference BGP community tag to the prefixes for secondary connection.
Explanation

For private and transit virtual interfaces, AWS Direct Connect local-preference BGP communities control the preferred AWS-to-on-premises path. Community 7224:7300 is high preference and 7224:7100 is low preference; assigning them to the primary and secondary advertised prefixes, respectively, creates active-passive failover. AWS documents this exact high/low community pattern for active-passive Direct Connect configurations.

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