Connect data centers by using CEN - Cloud Enterprise Network

This topic describes how to connect data centers by using route maps of Cloud Enterprise Network (CEN).

Prerequisites

Before you configure route maps, make sure that the following requirements are met:

The data centers are connected to Alibaba Cloud by using Express Connect circuits. For more information, see Create a dedicated connection over an Express Connect circuit.
A CEN instance is created. Network instances that you want to connect are attached to the CEN instance. For more information, see Create a CEN instance and Attach network instances to a CEN instance.
A bandwidth plan is purchased and the bandwidth for cross-region communication is allocated. For more information, see Purchase a bandwidth plan and Set the cross-region bandwidth.

Background information

The system automatically adds a default route map to the transit router of a CEN instance. The priority value of the default route map is 5000 and the action policy is deny. This route map forbids virtual border routers (VBRs) and Cloud Connect Network (CCN) instances from communicating with those that are attached to the same CEN instance. However, in some scenarios, you may need to allow the VBRs and CCN instances to communicate with those that are attached to the same CEN instance.

Notice If you delete the default route map, routing loops may occur. Proceed with caution.

As shown in the preceding figure, Data Center 1 is located in the China (Beijing) region and connected to Alibaba Cloud by using VBR 1. Data Center 2 is located in the China (Hangzhou) region and connected to Alibaba Cloud by using VBR 2. VBR 1 and VBR 2 are attached to the CEN instance. By default, Data Center 1 and Data Center 2 cannot communicate with each other. To enable the communication between Data Center 1 and Data Center 2, you can configure route maps for the VBRs by performing the following steps:

Step 1: Configure a route map that allows Date Center 1 to access Data Center 2

Log on to the CEN console.
On the Instances page, find the CEN instance that you want to manage and click the ID of the instance.
On the instance details page, find the region where you want to add a route map and click the ID of the transit router deployed in the region.
On the details page of the transit router, click the Route Table tab and click Route Maps.
On the Route Maps page, click Add Route Map. Set the following parameters and click OK:
- Route Map Priority: Enter a priority value for the route map. A lower value indicates a higher priority. In this example, 20 is entered.
- Description: Enter a description for the route map. This parameter is optional.
- Region: Select the region to which the route map is applied. In this example, China (Beijing) is entered.
- Transmit Direction: Select the direction of the route map. In this example, Export from Regional Gateway is selected.
- Match Conditions: Set the match conditions of routes. The following match conditions are set:
  - Source Instance IDs: Select the ID of VBR 2.
  - Destination Instance IDs: Select the ID of VBR 1.
- Action Policy: Select the action that you want to perform on a route when the route meets all match conditions. In this example, Permit is selected.
After the route map is added, you can view the route that allows Data Center 1 to access Data Center 2 on the Routing Information tab.

Step 2: Add a route map that allows Data Center 2 to access Data Center 1

In the left-side navigation pane, click Instances.
On the Instances page, find the CEN instance that you want to manage and click the ID of the instance.
On the instance details page, find the region where you want to add a route map and click the ID of the transit router deployed in the region.
On the details page of the transit router, click the Route Table tab and click Route Maps.
On the Route Maps page, click Add Route Map. Set the following parameters and click OK:
- Route Map Priority: Enter a priority value for the route map. A lower value indicates a higher priority. In this example, 20 is entered.
- Description: Enter a description for the route map. This parameter is optional.
- Region: Select the region to which the route map is applied. In this example, China (Hangzhou) is entered.
- Transmit Direction: Select the direction of the route map. In this example, Export from Regional Gateway is selected.
- Match Conditions: Set the match conditions of routes. The following match conditions are set:
  - Source Instance IDs: Select the ID of VBR 1.
  - Destination Instance IDs: Select the ID of VBR 2.
- Action Policy: Select the action that you want to perform on a route when the route meets all match conditions. In this example, Permit is selected.
After the route map is added, you can view the route that allows Data Center 2 to access Data Center 1 on the Routing Information tab.

Step 3: Test the connectivity between Data Center 1 and Data Center 2

Open the command prompt on a PC in Data Center 1.
Run the ping command to ping the IP address of a PC in Data Center 2 to test the connectivity.
The result indicates that the PC in Data Center 1 can access the PC in Data Center 2.
Open the command prompt on a PC in Data Center 2.
Run the ping command to ping the IP address of a PC in Data Center 1 to test the connectivity.
The result indicates that the PC in Data Center 2 can access the PC in Data Center 1.