A company heavily relies on AWS Direct Connect for hybrid connectivity, utilizing multiple Direct Connect gateways (DXGWs) to connect various on-premises locations to multiple VPCs across different AWS regions. The network team needs to implement a cost optimization strategy to reduce data transfer costs over these Direct Connect links, specifically for traffic between VPCs in different regions that are connected to the same DXGW. Which approach is the most cost-effective for inter-region VPC traffic when using Direct Connect Gateways?
- ARoute inter-region VPC traffic through the on-premises network.
- BUtilize VPC peering connections between VPCs in different regions instead of Direct Connect.
- CUse AWS Transit Gateway peering to connect VPCs across regions.
- DEnsure all inter-region VPC traffic connected to the same DXGW uses the AWS global network.
Show answer & explanationAnswer & explanation
Correct answer: D. Ensure all inter-region VPC traffic connected to the same DXGW uses the AWS global network.
When VPCs in different regions are associated with the same Direct Connect Gateway, traffic between these VPCs can traverse the AWS global network without leaving AWS. This inter-region data transfer over the AWS global network, when initiated from a Direct Connect Gateway, is significantly more cost-effective than routing it back to on-premises (A), using separate VPC peering (B), or even Transit Gateway peering (D) which has its own data transfer costs. The key is that the traffic stays within AWS's optimized backbone.
Why the other options are wrong
- A. Routing inter-region VPC traffic through on-premises would incur additional Direct Connect outbound data transfer costs and add latency, making it less cost-effective.
- B. VPC peering connections incur standard inter-region data transfer costs, which are generally higher than the optimized path through a Direct Connect Gateway using the AWS global network for inter-VPC traffic.
- C. AWS Transit Gateway peering connects TGWs in different regions. While it's a valid way to connect VPCs across regions, the data transfer costs associated with TGW peering are typically higher than the optimized path provided by a single DXGW for inter-VPC traffic within AWS, especially when the DXGW is already in place.
DXGW Inter-Region VPC Traffic Cost
Inter-region data transfer between VPCs associated with the *same* Direct Connect Gateway leverages the AWS global network at optimized, lower costs.
- Applies to VPCs in different regions
- VPCs must be associated with the same DXGW
- Traffic stays within AWS global network
- Cost-effective for inter-VPC traffic
Memory trick: Same DXGW, different VPCs: AWS backbone is the cheapest superhighway.