After you connect a network instance to a transit router, you can create an associated forwarding correlation to associate the network instance connection with a route table. After you configure an associated forwarding correlation, the transit router forwards the traffic of the network instance based on the route table.

Prerequisites

An Enterprise Edition transit router is used. For more information about how to check the edition of a transit router, see View the edition of a transit router.

Background information

How it worksThe preceding figure shows an example on how associated forwarding works. In this example, the transit router in the China (Hangzhou) region is connected to VPC1 and VPC2. The VPC1 connection is associated with Route Table A, and the VPC2 connection is associated with Route Table B. A client in VPC1 wants to access a server in VPC2. The IP address of the server falls into the CIDR block 10.1.1.0/24. The following table shows the process.
No. Description
① A server in VPC1 initiates a request to a server in VPC2. The IP address of the server in VPC2 falls into the CIDR block 10.1.1.0/24.
② The VPC1 connection is associated with Route Table A. After the transit router receives the request from VPC1, the transit router queries whether Route Table A contains a route that points to the CIDR block 10.1.1.0/24.
  • If the route exists, the request from VPC1 is forwarded to the next hop of 10.1.1.0/24.
  • If the route does not exist, VPC1 cannot access the client in 10.1.1.0/24.
③ The transit router queries the information about the route that points to 10.1.1.0/24 in Route Table A and forwards the request to VPC2.
④ The VPC2 connection receives the request and returns an echo reply packet to VPC1.
⑤ The VPC2 connection is associated with Route Table B. After the transit router receives the echo reply packet from VPC2, the transit router queries whether Route Table B contains a route that points to 192.168.1.0/24.
  • If the route exists, the echo reply packet is forwarded to the next hop of 192.168.1.0/24.
  • If the route does not exist, VPC1 cannot send the echo reply packet to the client in VPC2.
⑥ The transit router queries the information about the route that points to 192.168.1.0/24 in Route Table B and forwards the echo reply packet to VPC1.

Create an associated forwarding correlation

  1. Log on to the CEN console.
  2. On the Instances page, find the CEN instance that you want to manage and click the instance ID.
  3. Choose Basic Settings > Transit Router, find the transit router that you want to manage, and then click the ID of the transit router.
  4. On the details page of the transit router, click the Route Propagation tab.
  5. 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 Table Association tab.
  6. On the Route Table Association tab, click Create Association. In the Add Association dialog box, set the following parameters and click OK.
    Parameter Description
    Route Table By default, the current route table is selected.
    Transit Router By default, the current transit router is selected.
    Association Select the network instance connection that you want to associate with the route table.

    Then, the transit router forwards network traffic based on the associated route table.

Delete an associated forwarding correlation

  1. Log on to the CEN console.
  2. On the Instances page, find the CEN instance that you want to manage and click the instance ID.
  3. Choose Basic Settings > Transit Router, find the transit router that you want to manage, and then click the ID of the transit router.
  4. On the details page of the transit router, click the Route Propagation tab.
  5. 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 Table Association tab.
  6. On the Route Table Association tab, find the network instance connection and click Delete in the Actions column.
  7. In the Delete Association message, confirm the information and click OK.

References