Use custom route tables to customize network connectivity-Cloud Enterprise Network(CEN)-阿里云帮助中心

Custom route tables let you control how an Enterprise Edition transit router forwards traffic from connected network instances. You can associate network instance connections with a custom route table, then add custom routes, attach prefix lists, and create aggregate routes to shape traffic flow.

Background

When you create a transit router, the system automatically creates a system (default) route table. Enterprise Edition transit routers also support custom route tables, while Basic Edition transit routers do not. For information about how to view the edition of a transit router, see View the edition of a transit router instance.

On an Enterprise Edition transit router, the system route table and custom route tables are isolated from each other:

The system automatically creates a system route table when you create a transit router instance.
You must manually create a custom route table. A custom route table is similar to a virtual routing and forwarding (VRF) instance on a traditional router. It is isolated from the system route table and other custom route tables to provide access isolation.

After you connect a network instance to a transit router, you can associate the connection with a custom route table through associated forwarding. The transit router then forwards traffic from the network instance by looking up routes in that custom route table. You can further customize connectivity by adding custom routes, attaching prefix lists, and creating aggregate routes.

Create a custom route table

Log on to the CEN console.
On the CEN Instance page, click the ID of the CEN instance that you want to manage.
Go to the Basic Information > Transit Router tab and click the ID of the transit router that you want to manage.
On the details page of the transit router, click the Route Table tab.

In the navigation pane on the left, click Create Route Table. In the Create Route Table dialog box, configure the parameters and click OK.

Parameter	Description
Transit Router	Select the target transit router. The ID of the selected transit router is displayed automatically.
Name	Enter a name for the custom route table.
Description	Enter a description for the custom route table.
Tag	Add a tag to the custom route table. Tag key: cannot be an empty string. The key can be up to 64 characters in length and cannot start with `aliyun` or `acs:`. It cannot contain `http://` or `https://`. Tag value: can be an empty string. The value can be up to 128 characters in length and cannot start with `aliyun` or `acs:`. It cannot contain `http://` or `https://`. You can add multiple tags to a custom route table. For more information about tags, see Tags.
Multi-region ECMP Routing	Enables multi-region ECMP routing for routes learned from virtual border routers (VBRs). This feature is disabled by default. If an Enterprise Edition transit router learns routes with the same destination CIDR block from multiple VBRs, and all other route attributes are identical, the system by default forwards traffic to the VBR in the alphabetically first region. If you enable this feature, the transit router treats these as equal-cost routes and uses equal-cost multipath (ECMP) to distribute traffic among them. For more information, see Multi-region VBR equal-cost routing. To enable this feature, click the switch. In the dialog box that appears, carefully read the risk notice and click OK.

View route tables: Enterprise Edition transit router

Log on to the CEN console.
On the CEN Instance page, click the ID of the CEN instance that you want to manage.
Go to the Basic Information > Transit Router tab and click the ID of the transit router that you want to manage.
On the details page of the transit router, click the Route Table tab.
In the navigation pane on the left, click the ID of the target route table.
On the route table details page, you can view the following information:
- View the routes in the transit router. For more information, see View the routes of an Enterprise Edition transit router.
- View existing associated forwarding connections. For more information, see Associated forwarding.
- View existing route learning connections. For more information, see Route learning.
- View existing routing policies. For more information, see Routing policies (legacy, for TR only).
- View existing prefix lists. For more information, see Prefix lists.
- View existing aggregate routes. For more information, see Aggregate routes.

View route tables: Basic Edition transit router

Log on to the CEN console.
On the CEN Instance page, click the ID of the CEN instance that you want to manage.
Go to the Basic Information > Transit Router tab and click the ID of the transit router that you want to manage.
On the details page of the transit router, click the Route Table tab to view the following information.
- View the routes in the transit router. For more information, see View the routes of a Basic Edition transit router.
- View existing routing policies. For more information, see Routing policies (legacy, for TR only).

Delete a custom route table

You can delete a custom route table that is no longer needed. The system route table cannot be deleted. Before you delete a custom route table, make sure the following conditions are met:

There are no associated forwarding connections in the custom route table. For more information, see Delete an associated forwarding connection.
There are no route learning connections in the custom route table. For more information, see Delete a route learning connection.
There are no custom routes in the custom route table. For more information, see Delete a custom route of an Enterprise Edition transit router.
No prefix list is associated with the custom route table. For more information, see Disassociate a prefix list.
There are no aggregate routes in the custom route table. For more information, see Delete an aggregate route.

Log on to the CEN console.
On the CEN Instance page, click the ID of the CEN instance that you want to manage.
Go to the Basic Information > Transit Router tab and click the ID of the transit router that you want to manage.
On the details page of the transit router, click the Route Table tab.
In the navigation pane on the left, click the ID of the target custom route table.
In the Route Table Details section, click Delete.
In the Delete Route Table dialog box, click OK.

API reference

CreateTransitRouterRouteTable: Creates a custom route table for an Enterprise Edition transit router.
UpdateTransitRouterRouteTable: Modifies the name and description of a route table for an Enterprise Edition transit router.
ListTransitRouterRouteTables: Queries the route tables of an Enterprise Edition transit router.
DeleteTransitRouterRouteTable: Deletes a custom route table of an Enterprise Edition transit router.