This topic describes how to migrate a VPC from a peering connection in Express Connect to a Cloud Enterprise Network (CEN) instance. CEN allows you to enable communication between VPCs and between VPCs and on-premises data centers by using internal network connections. CEN automatically learns and distributes routes, and quickly adapts to network changes. This improves the quality of cross-network communication.

Warning Before you freeze or delete the router interfaces, make sure that the routes for both the local and peer VPCs in the peering connection are migrated.

Preparations

If you want to migrate a VPC to an existing CEN instance, make sure that the overlapping routing function is enabled.

Note If the overlapping routing function is not enabled for the CEN instance, enable it first.
Overlapping routing function

Procedure

To migrate a VPC from a peering connection to a CEN instance, perform the following steps:

Note Before the migration, make sure that you complete the preparations.
  1. Log on to the CEN console.
  2. On the Instances page, find the required CEN instance and click its ID.
  3. On the Networks tab, click Attach Network and attach the VPC that you want to migrate. For more information, see Attach networks.
  4. If you want to communicate across regions, purchase a bandwidth plan and configure the bandwidth for the communication.

    For more information, see Set a cross-region bandwidth.

  5. If you have added routes that point to high-availability virtual IP addresses (HAVIPs) or IP addresses of ECS instances and VPN gateways, go to the VPC console and advertise these routes to the CEN instance based on your connection requirements.Advertise routes
  6. Log on to the CEN console and click the ID of the required CEN instance. Then, click the Routes tab to view the route information. After you attach the VPC to the CEN instance, make sure that the routes do not conflict.

    The static routes that are configured in the peering connection have higher priorities than the dynamic routes of the CEN instance. Specifically, if a static route is configured in the peering connection, CEN does not learn routes that are more specific than the static route and have the same destination as the static route. We recommend that you split static routes of the peering connection and delete them after CEN learns the routes. This ensures smooth migration.

    In the following figure, the route to 172.16.1.0/24 in the CEN instance is more specific than the route to 172.16.0.0/16 in the peering connection. Therefore, the two routes are in conflict. Routes
    • If you can tolerate a transient network interruption during the migration, delete the route to 172.16.0.0/16 in the VPC console. Then, the route in the CEN instance automatically takes effect.

      The duration of the network interruption increases as the number of CEN routes increases. For important business scenarios, we recommend that you use the following method to smoothly migrate the VPC.

    • If you want to smoothly migrate the VPC, split the route in the peering connection into routes more specific than the route to 172.16.1.0/24 in the CEN instance. For example, split the route to 172.16.0.0/16 in the peering connection into two routes, one to 172.16.1.0/25 and the other to 172.16.1.128/25.
      1. Log on to the VPC console and find the route table to which the route you want to split belongs.
      2. Click Add Route Entry to add two routes in which the destination CIDR blocks are 172.16.1.0/25 and 172.16.1.128/25 and the next hops are the router interface of the peering connection.Add Route Entry
      3. Find the route to 172.16.0.0/16 and click Delete in the Actions column.Route information
      4. Click Refresh to check whether the routes in the CEN instance take effect.Smooth migration
      5. After the routes in the CEN instance take effect, delete the routes to 172.16.1.0/25 and 172.16.1.128/25. The smooth migration is complete.