Override DefaultRoute

[mancinifm]

We have set DefaultRoute hub parameter to All-Traffic (0/0), however for one of our VPCs we wish to override this so that the tagged subnet RT points to a more specific network.

Is this possible?

[gsingh04]

Hello @mancinifm thank you for your query.

There is a CloudFormation parameter which you can use to change the default configuration. Review parameter under VPC Route Table Settings, Choose the type of destination for target Transit Gateway. This parameter can be adjusted for Custom-Destinations. With custom destinations, you can provide either CIDR blocks or managed prefix-lists. See more details here.

One thing to note, the change will be applied to all VPCs moving forward.

[mancinifm]

Thank you for the info.

It sounds like STNO intends for all VPCs in the solution to use the same CIDR for the TGW route, and the only way to support having this route differ between VPCs is to set DefaultRoute to Configure-Manually and for each new VPC attached, manually set the route.

What would be nice is if there was an additional tag for tagged subnets called something like tgw-cidr which allows me to override the default value on a per-VPC basis.

However this is not a deal breaker and I am happy for you to close this issue if my understanding of the situation is correct.

Appreciate your response.