How to migrate VBRs from peering connections to CEN - Cloud Enterprise Network

This guide describes how to smoothly migrate a virtual border router (VBR) from an Express Connect peering connection to Cloud Enterprise Network (CEN). CEN establishes private communication channels between VPCs, and between VPCs and data centers. By automatically distributing and learning routes, CEN accelerates network convergence, improves the quality of cross-network communication, and enables seamless connectivity for all your network resources.

Prerequisites

A CEN instance is required. For more information, see Create a CEN instance.

Procedure

Follow these steps to migrate a VBR from a peering connection to CEN.

Warning

Ensure that the Express Connect routes on both ends of the peering connection are fully migrated before you disable or delete the router interfaces.

If a health check is configured for the VBR, first delete the health check in the Express Connect console. For more information, see Configure and manage a health check.
Log on to the CEN console.
On the CEN Instance page, click the ID of the CEN instance.
Select the type of instance to attach and click the icon next to the target instance type.
On the Create Intra-Region Connection page, configure the required information to attach the target VPC and VBR instances. For more information, see Attach a VPC and Attach a VBR.
To enable cross-region communication, purchase a bandwidth plan for the CEN instance and configure inter-region bandwidth.
For more information, see Use a bandwidth plan and Create an inter-region connection.
If the VPC contains routes that point to resources such as ECS instances, VPN gateways, or High-availability Virtual IP addresses (HaVips), publish these routes to CEN from the VPC console.
If your data center needs to access Alibaba Cloud services such as OSS and PrivateZone, configure the access in the CEN console.
For more information, see Enable access to cloud services and Enable access to PrivateZone.
Log on to the CEN console. On the details page of the transit router in the target region, click the Network Instance Route Table tab to review the route configuration of the target instance. Ensure that no route conflicts exist after the VBR and VPC are attached.
Static routes configured for an Express Connect peering connection take precedence over dynamic routes learned by CEN. This means that if a static Express Connect route exists, CEN cannot learn a route that is identical to or more specific than the static route. In this case, split the static route to ensure a smooth migration. After CEN learns the new routes, you can delete the split routes.
For example, the CEN route 192.168.1.0/24 is more specific than the route 192.168.0.0/16 that points to Express Connect. This causes a route conflict.
- For a quick cutover, delete the Express Connect route 192.168.0.0/16. The CEN route then automatically takes effect.
  The duration of the service interruption is proportional to the number of CEN routes. For mission-critical services, use the smooth migration method.
- For a smooth migration, split the Express Connect route 192.168.0.0/16 into routes that are more specific than the CEN route 192.168.1.0/24. For example, split 192.168.0.0/16 into two more specific routes: 192.168.1.0/25 and 192.168.1.128/25.
  1. In the Express Connect console, on the VBR details page, click Route Entry to open the VBR route table.
  2. Click Add Route Entry to add two routes. Set the destination CIDR blocks to 192.168.1.0/25 and 192.168.1.128/25, and set the next hop to the VPC.
  3. If you use BGP, advertise the routes for 192.168.1.0/25 and 192.168.1.128/25.
  4. Delete the Express Connect route 192.168.0.0/16.
  5. Click Refresh and verify that the CEN routes are in effect. After the refresh, the route table shows that the CEN route entry whose destination CIDR block is 192.168.1.0/24 and whose next hop type is Cloud Enterprise Network is in effect. At the same time, the status of the existing physical Express Connect route entry whose destination CIDR block is 10.1.0.0/16 is displayed as Conflict.
  6. In the VBR route table, delete the two specific routes 192.168.1.0/25 and 192.168.1.128/25. If you use BGP, withdraw the advertisements for these BGP routes.
  7. In the CEN console, configure a health check for the migrated VBR. For more information, see Configure a health check for a VBR.