Why Can't VPCs Connected Through an Enterprise Router Communicate?

Symptom

After the VPCs are attached to an enterprise router, routes pointing to the enterprise router have been configured in the VPC route tables, but the VPCs still cannot communicate with each other.

Fault Cause

A route pointing to the enterprise router is configured as the default route (0.0.0.0/0) in the VPC route table. If an ECS in the VPC has an EIP bound, a policy-based route with the destination of 0.0.0.0/0 is automatically added for the ECS. The priority of this policy-based route is higher than that of the default route pointing to the enterprise router in the VPC route table. As a result, traffic is forwarded to the EIP instead of the enterprise router.

Because the default route (0.0.0.0/0) has the lowest priority in the VPC route table, you should configure a more specific route to the enterprise router to ensure it takes effect. For more information, see Route Priority.