Enable a route table of an Enterprise Edition transit router to learn routes from network instances-Cloud Enterprise Network(CEN)-阿里云帮助中心

Limitations

Route propagation is supported only by route tables of an Enterprise Edition transit router. To check the edition of a Transit Router, see View the edition of a Transit Router.

Example

As shown in the figure, two VPCs are created in the China (Hangzhou) region and connected to the same Transit Router.

With route propagation enabled, the Transit Router learns the system routes from both VPCs and adds them to its default route table.

If the connections of the two VPCs are associated with the default route table of the Transit Router, traffic from the VPCs is forwarded to the corresponding next hop based on the routes automatically learned by the Transit Router.

Route propagation from network instances

A route table of an Enterprise Edition transit router can learn routes from multiple network instance connections, and a single network instance connection can propagate its routes to multiple route tables.

After you enable route propagation from a network instance connection to a route table of an Enterprise Edition transit router, the network instance propagates the following routes to the route table by default:

Network instance connection	Corresponding network instance	Automatically propagated routes
VPC connection	VPC	The system routes of the VPC. To propagate custom routes from the system route table of a VPC to a route table of an Enterprise Edition transit router, you must publish them to Cloud Enterprise Network (CEN). For more information, see Publish routes to a Transit Router. Custom routes in custom route tables of a VPC cannot be published to Cloud Enterprise Network (CEN).
VBR connection	virtual border router (VBR)	Routes from the Custom Route Entry tab of the VBR that use an Express Connect circuit as the next hop. Routes on the BGP Route Entry tab of the VBR. To find these routes, see Add and manage routes.
ECR connection	Express Connect Router (ECR)	Routes whose next hop is a VBR.
VPN connection	IPsec-VPN connection	Routes from the destination and BGP route tables of the IPsec-VPN connection.
Inter-region connection	Transit Router	If the peer is an Enterprise Edition transit router and route synchronization is enabled, routes from the associated peer route table are automatically propagated to the current route table. If the peer is a Basic Edition transit router and route synchronization is enabled, routes from the peer's route table are automatically propagated to the current route table.

Enable route propagation

Method 1: When creating a network instance connection

When you create a network instance connection, select Propagate system routes to transit router route table in the Advanced Settings section. This enables route propagation, allowing the Transit Router's default route table to learn routes from the network instance.

The following figure shows an example of creating a VPC connection.

For more information, see Create a VPC connection, Create an ECR connection, Create a VBR connection, Create a VPN connection, and Create an inter-region connection.

Method 2: After creating a network instance connection

You can also enable route propagation in the following scenarios:

You did not select "Propagate System Routes to Default Route Table of Transit Router" when creating the network instance connection.
You want a custom route table in the Transit Router to learn routes from a network instance.

Follow these steps:

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 left-side section, click the ID of the route table that you want to manage. On the details page of the route table, click the Route Propagation tab.

On the Route Propagation tab, click Enable Route Propagation. In the Enable Route Propagation dialog box, configure the following parameters and click OK.

Parameter	Description
Route Table	The system selects the current route table by default.
Transit Router ID	The system selects the current Transit Router instance by default.
Attachment	Select the network instance connection from which you want the route table to learn routes. After route propagation is enabled, the network instance automatically propagates routes to the route table. You can view these routes on the Route Entry tab.

Disable route propagation

When you disable route propagation, the routes propagated from the network instance to the route table of the Enterprise Edition transit router are automatically withdrawn.

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 left-side section, click the ID of the route table that you want to manage. On the details page of the route table, click the Route Propagation tab.
On the Route Propagation tab, find the target network instance connection and click Delete in the Actions column.
In the Disable Route Propagation dialog box, confirm the information and click OK.

Related APIs

EnableTransitRouterRouteTablePropagation: Enables route propagation.
ListTransitRouterRouteTablePropagations: Queries the route propagation settings of a transit router's route table.
DisableTransitRouterRouteTablePropagation: Disables route propagation.