Load Balancing over Direct Connect Gateway

Question

Reference: https://www.amazonaws.cn/en/directconnect/faqs/

Q. I have two Direct Connect connections, both 1G, I want all incoming traffic into my network load balanced across these two connections, can I use community based routing to achieve such load balancing across the locations?

Yes, you can use community based routing to enable load balancing across Direct Connect locations; To do so, any prefixes requiring load-balancing must be marked with the same communities.

The way I understand is, if 10.10.0.0/16 was advertised by 2 DX connected to same or different DXGW, the DXGW(s) install this route in the Transit Gateway route table attached to VPCs saying to get to 10.10.0.0/16 the next hop is . However, if both DX attachments are advertising same routes and Transit Gateway does not support ECMP on DX, how would the load balancing work. AFAIK, Transit Gateway ECMP is only for IPSec VPN.

Answer 1

Reference:- Architecture diagram

From the above link, we can see that Transit-GW association's are ending with VPC's and DX-Gateway, so usually load balancing definitions are done via VIF definition on DX Connections.

• Moreover if you the see the BGP peer definition of Private Virtual Interface and Transit Virtual Interface are almost same .
• To better understand, just imagine 2 Transit virtual interfaces for each DX Connection terminating on same DX-Gateway on the other side.

I guess, load balancing should be the same as how it used to be with Private VIF's and DX-Gateway combination (Here Transit Virtual interface instead of Private VIF's)

Answer 2

Thanks @jestadi. Your answer is correct and I confirmed it by 2 sources. Look at the comment section on the edge-cloud blog

Also, its written on page 143/144 of the AWS Certified Advanced Networking Official Study Guide