Each VPC created in AWS comes with a Default Route Table that can be managed, but not destroyed. This is an advanced resource, and has special caveats to be aware of when using it. Please read this document in its entirety before using this resource. It is recommended you do not use both aws_default_route_table to manage the default route table and use the aws_main_route_table_association, due to possible conflict in routes.

The aws_default_route_table behaves differently from normal resources, in that Terraform does not create this resource, but instead attempts to "adopt" it into management. We can do this because each VPC created has a Default Route Table that cannot be destroyed, and is created with a single route.

When Terraform first adopts the Default Route Table, it immediately removes all defined routes. It then proceeds to create any routes specified in the configuration. This step is required so that only the routes specified in the configuration present in the Default Route Table.