How to stop advertising default route in s2s VPN with BGP

Question

Hi All,
I have multiple s2s VPN connections from AWS (built on Transit Gateway) to other clouds (GCP and Azure). I have set up the tunnel options to only advertise specific subnets on the AWS side, but I still see 0.0.0.0/0 route is being advertised from AWS to others for example GCP! how can I stop that? this is causing an issue because I do not want in any outage scenario the other end (GCP or Azure) exits from AWS! I'd appreciate any help

Tushar_J · Answer

The way to control route propagation over BGP for VPN is with TGW route tables. You can create a new TGW route table just for the VPN tunnel(s) and then only propagate the routes that are needed.

mml · Answer

AWS will advertise 0.0.0.0/0 if it exists in the TGW routing table just like any other route. You can create a filter on your CGW under the BGP neighbor definition to filter 0.0.0.0/0 route. This way, you will continue receiving and installing all the desired routes from the TGW except 0.0.0.0/0 route.

How to stop advertising default route in s2s VPN with BGP

Relevant content