An enterprise has a multi-account AWS environment with a Transit Gateway (TGW) deployed in… — AWS Certified Solutions Architect - Professional

An enterprise has a multi-account AWS environment with a Transit Gateway (TGW) deployed in the $us-east-1$ Region. The enterprise requires high-availability hybrid connectivity to its on-premises data center. To achieve this, the enterprise establishes two AWS Direct Connect (DX) connections:
- Connection A: A primary $10\text{ Gbps}$ DX connection at a Virginia DX location.
- Connection B: A backup $1\text{ Gbps}$ DX connection at a Chicago DX location.

Both connections terminate on the same customer gateway router on-premises. The Solutions Architect creates a Transit Virtual Interface (Transit VIF) for each connection and associates them with a single Direct Connect Gateway (DXGW), which is attached to the TGW in $us-east-1$ .

The enterprise has the following traffic requirements:
- Requirement 1: Traffic from AWS to the on-premises network must prefer Connection A. If Connection A fails, traffic must fail over to Connection B.
- Requirement 2: Traffic from the on-premises network to AWS must prefer Connection A. If Connection A fails, traffic must fail over to Connection B.

Which combination of BGP routing configurations will meet these requirements while preventing asymmetric routing?

For AWS-to-on-premises traffic, configure the customer gateway to advertise the on-premises prefixes to AWS with the BGP community $7224:7300$ over Connection A, and with the BGP community $7224:7100$ over Connection B. For on-premises-to-AWS traffic, configure the customer gateway to set a higher local preference for routes received over Connection A containing the BGP community $7224:8100$ compared to routes received over Connection B containing the BGP community $7224:8200$ .Cevap
B
For AWS-to-on-premises traffic, configure the customer gateway to advertise the on-premises prefixes to AWS with the BGP community $7224:8100$ over Connection A, and with the BGP community $7224:8200$ over Connection B. For on-premises-to-AWS traffic, configure the customer gateway to set a higher local preference for routes received over Connection A containing the BGP community $7224:7300$ compared to routes received over Connection B containing the BGP community $7224:7100$ .
C
For AWS-to-on-premises traffic, configure the customer gateway to advertise the on-premises prefixes with a shorter AS path over Connection A, and a longer AS path over Connection B using AS-Path prepending. For on-premises-to-AWS traffic, associate a Route 53 Private Hosted Zone with Connection A to dynamically resolve the on-premises DNS endpoints, while keeping Connection B as a standby DNS resolver.
D
For AWS-to-on-premises traffic, configure a static route on the Transit Gateway route table pointing to Connection A as the primary target and Connection B as the secondary target. For on-premises-to-AWS traffic, deploy a NAT Gateway in a transit VPC associated with the Transit Gateway to route outbound traffic preferentially through Connection A.

Cevap

Configure the customer gateway to advertise on-premises prefixes with the BGP community

7224:7300

over Connection A and

7224:7100

over Connection B, and configure the customer gateway to set a higher local preference for routes received over Connection A containing the BGP community

7224:8100

compared to routes received over Connection B containing the BGP community

7224:8200

The correct configuration uses BGP communities to influence routing in both directions. For AWS-to-on-premises traffic, the customer gateway uses the communities

7224:7300

(high preference) and

7224:7100

(low preference) to instruct the AWS Direct Connect Gateway which path to prefer. For on-premises-to-AWS traffic, AWS advertises prefixes with

7224:8100

(indicating the local region, Virginia/us-east-1) over Connection A and

7224:8200

(indicating same continent, Chicago) over Connection B. By mapping these communities to a higher local preference on the customer gateway for Connection A, traffic flows symmetrically over Connection A and dynamically fails over to Connection B if Connection A goes offline.

Adım Adım Çözüm

Configure the customer gateway to advertise the on-premises prefixes with specific BGP communities to AWS.

The customer gateway advertises prefixes with

7224:7300

over Connection A and

7224:7100

over Connection B.

This influences the Direct Connect Gateway's path selection for AWS outbound traffic, prioritizing Connection A.

Configure the customer gateway to evaluate incoming BGP communities advertised by AWS.

The customer gateway identifies routes with the community

7224:8100

on Connection A and

7224:8200

on Connection B.

AWS advertises local region routes with

7224:8100

and same-continent routes with

7224:8200

to help the customer determine route proximity.

Configure BGP local preference on the customer gateway based on the received communities.

A higher local preference is assigned to routes received with

7224:8100

, directing on-premises-to-AWS traffic over Connection A.

This alignment prevents asymmetric routing and guarantees symmetric traffic flows over the primary connection.

Anahtar Kavram

Symmetric hybrid routing using BGP communities over AWS Direct Connect and Transit Gateway

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