AWS Transit Gateway through BGP propagation and routing behavior

Question

When I added the VPN to a transit gateway attachment, the VPN route was automatically propagated through BGP to the routing table on the transit gateway.
1. Is this an expected behavior for routes to propagate automatically when the routes are added to the attachment? This can cause a communication problem. The IP CIDR that is in use by the on-premise server engine might conflict with the VPC CIDR range.
2. Is there a way to disable the route propagation setting for BGP on the routing table of the transit gateway?

Accepted Answer

If you've enabled the "Default route table propagation" option on your transit gateway (TGW), it will automatically propagate transit gateway attachments (like VPN) using the default route table. Note that this setting is enabled by default. To disable the "Default route table propogation" option, create a new transit gateway with the option disabled. You won't be able to disable this option by editing the TGW configurations.

If you've disabled the "Default route table propogation" option when you create your transit gateway, make sure to specify which route tables you want to propagate the routes to or from the VPN attachment.

AWS Transit Gateway through BGP propagation and routing behavior

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