Process of Using Enterprise Router to Migrate the Network Set Up Through VPC Peering

Step 1: Create Cloud Resources

1. Create an enterprise router. (Only one enterprise router is required in a region.)
2. Create a verification subnet in each VPC. These subnets cannot communicate with each other through VPC peering connections, but can communicate through the enterprise router to verify the communications between the VPCs and enterprise router during the migration.
3. Create an ECS in each verification subnet. Log in to the ECS and use ping to verify communications between the VPCs and enterprise router.

Step 2: Create VPC Attachments and Add Routes

1. Create VPC attachments to attach the three VPCs to the enterprise router.

   Do not enable Auto Add Routes and manually add routes with destinations set to large CIDR blocks in the VPC route tables.

2. Check the routes in the enterprise router route table.

   In this example, Default Route Table Association and Default Route Table Propagation are enabled for the enterprise router, and routes with destinations set to VPC CIDR blocks are automatically added when you attach the VPCs to the enterprise router.

Step 3: Verify communications Between the VPCs and Enterprise Router

1. Add routes with the next hop set to the enterprise router in the VPC route tables. These routes are used to verify communications between the VPCs and enterprise router.
2. Log in to each ECS and use ping to verify connectivity.
3. After the verification, delete the routes, ECSs, and subnets that are used for verifying communications.

Step 4: Add Routes to VPC Route Tables

1. Add routes for temporary communications to the VPC route tables. These routes ensure that traffic is not interrupted when original routes added for VPC peering connections are deleted.
2. Add routes with the next hop set to the enterprise router in the VPC route tables. These routes are used to verify communications between the VPCs and enterprise router.

Step 5: Perform the Migration

Delete the original routes with the next hop set to the VPC peering connection from the VPC route tables.

During the migration, check the service traffic in real time. If traffic is interrupted, add the deleted routes immediately.

Step 6: Delete the Original VPC Peering Connections

After you have deleted original routes and verified that services are running properly, delete the VPC peering connections. This will also delete the routes for temporary communications from the VPC route tables.