You can create a custom route table in a virtual private cloud (VPC) and add custom routes to the custom route table. Then, you can associate the custom route table with a vSwitch to control the traffic of the vSwitch. This facilitates network management. The preceding operations are used to perform subnet routing.

Background information

Before you perform subnet routing, take note of the following limits:

  • Each VPC can contain at most 10 route tables including the system route table.
  • Each vSwitch can be associated with only one system route table or one custom route table.

Prerequisites

A VPC and a vSwitch are created. For more information, see Create an IPv4 VPC.

Step 1: Create a custom route table

  1. Log on to the VPC console.
  2. In the left-side navigation pane, click Route Tables.
  3. Select the region where you want to create a custom route table.
    The following table describes the regions that support custom route tables by default.
    Area Region
    Asia Pacific China (Qingdao), China (Zhangjiakou), China (Hohhot), China (Ulanqab), China (Shanghai), China (Heyuan), China (Guangzhou), China (Chengdu), China (Hong Kong), Japan (Tokyo), Singapore (Singapore), Australia (Sydney), Malaysia (Kuala Lumpur), Indonesia (Jakarta), and Philippines (Manila).
    Europe & Americas US (Silicon Valley), US (Virginia), Germany (Frankfurt), and UK (London)
    Middle East & India India (Mumbai) and UAE (Dubai)
    The custom route table feature is in public preview in the following regions. You can apply to participate in the public review.
    Area Region
    Asia Pacific China (Beijing), China (Hangzhou), and China (Shenzhen)
  4. On the Route Tables page, click Create Route Table.
  5. In the Create Route Table dialog box, set the following parameters and click OK.
    Parameter Description
    Resource Group Select the resource group to which the route table belongs.
    VPC Select the VPC to which the route table belongs.

    If the VPC contains an Elastic Compute Service (ECS) instance that belongs to one of the following instance families, you cannot create a custom route table for the VPC:

    ecs.c1, ecs.c2, ecs.c4, ecs.c5, ecs.ce4, ecs.cm4, ecs.d1, ecs.e3, ecs.e4, ecs.ga1, ecs.gn4, ecs.gn5, ecs.i1, ecs.m1, ecs.m2, ecs.mn4, ecs.n1, ecs.n2, ecs.n4, ecs.s1, ecs.s2, ecs.s3, ecs.se1, ecs.sn1, ecs.sn2, ecs.t1, and ecs.xn4.

    To create a custom route table, you must upgrade or release ECS instances that do not support advanced VPC features.
    Note If your VPC contains ECS instances of the preceding instance families and a custom route table is created, you must upgrade or release the ECS instances. Otherwise, the custom route table cannot work as expected. For more information, see Advanced VPC features.
    Name Enter a name for the route table.

    The name must be 2 to 128 characters in length and can contain digits, underscores (_), and hyphens (-). The name must start with a letter.

    Description Enter a description for the route table.

    The description must be 2 to 256 characters in length. The description cannot start with http:// or https://.

    After the custom route table is created, you can go to the Route Tables page to view the route table. Custom is displayed in the Route Table Type column of the route table. Custom route tablesThe following system route entries are automatically added to the custom route table:
    • A route entry whose destination CIDR block is 100.64.0.0/10. This route is used for communication among cloud resources within the VPC.
    • A route entry destined for the CIDR block of a vSwitch of the VPC to which the route table belongs. This route is used for communication between cloud resources within the vSwitch.
    For example, the CIDR block of your VPC is 192.168.0.0/16 and you created two vSwitches whose CIDR blocks are 192.168.1.0/24 and 192.168.0.0/24 in the VPC. The custom route table that you created for your VPC includes the following system route entries. The "-" sign in the following table indicates that the item is not applicable.
    Destination CIDR block Next hop Type
    100.64.0.0/10 - System route
    192.168.1.0/24 - System route
    192.168.0.0/24 - System route

Step 2: Add a custom route to the custom route table

  1. Log on to the VPC console.
  2. In the left-side navigation pane, click Route Tables.
  3. In the top navigation bar, select the region to which the custom route table belongs.
  4. On the Route Tables page, find the custom route table that you want to manage and click its ID.
  5. On the details page of the custom route table, choose Route Entry List > Custom Route, and click Add Route Entry.
  6. In the Add Route Entry panel, set the following parameters and click OK.
    Parameter Description
    Name Enter a name for the route entry.

    The name must be 2 to 128 characters, and can contain digits, underscores (_), and hyphens (-). The name must start with a letter.

    Destination CIDR Block Enter the CIDR block to which you want to forward traffic.
    Note If the selected route table is a system route table and the region to which the route table belongs supports IPv6, you can set Destination CIDR Block to IPv6 CIDR Block or IPv4 CIDR Block. For more information about the regions that support IPv6, see Regions that support VPC features.
    Next Hop Type Select the next hop type. Valid values:
    • ECS Instance: Traffic destined for the specified CIDR block is routed to the specified ECS instance.

      Select this type if you want to route traffic to a specified ECS instance for centralized traffic forwarding and management. For example, you can configure an ECS instance as the Internet-facing gateway to route traffic from other ECS instances to the Internet.

    • HaVip: Traffic destined for the specified CIDR block is routed to the high-availability virtual IP address (HAVIP) that you select.
    • VPN Gateway: Traffic destined for the specified CIDR block is routed to the specified VPN gateway.
    • NAT Gateway: Traffic destined for the specified CIDR block is routed to the specified NAT gateway.
    • Secondary ENI: Traffic destined for the specified CIDR block is routed to the specified secondary elastic network interface (ENI).
    • Transit Router: Traffic destined for the specified CIDR block is routed to the specified transit router. For more information about transit routers, see How transit routers work.
    • IPv6 Gateway: Traffic destined for the specified CIDR block is routed to the specified IPv6 gateway.
      Note If the selected route table is a system route table, the region to which the route table belongs supports IPv6, and Destination CIDR Block is set to IPv6 CIDR Block, you can set Next Hop Type to IPv6 Gateway, ECS Instance, or Secondary ENI.
    Resource Group Select the resource group to which the next hop belongs.

    This parameter is required only if you set Next Hop Type to ECS Instance or Secondary ENI.

    ECS Instance/HaVip/VPN Gateway/NAT Gateway/Secondary ENI/Transit Router/IPv6 Gateway Select an instance as the next hop.

Step 3: Associate the custom route table with a vSwitch

You can associate the custom route table with a vSwitch to manage the routes of the vSwitch. Each vSwitch can be associated with only one system route table or one custom route table.

  1. Log on to the VPC console.
  2. In the left-side navigation pane, click Route Tables.
  3. In the top navigation bar, select the region to which the route table belongs.
  4. On the Route Tables page, find the custom route table that you want to manage and click its ID.
  5. On the details page of the route table, click the Associated vSwitch tab and click Associate vSwitch.
  6. In the Associate vSwitch dialog box, select the vSwitch that you want to associate and click OK.
    On the Associated vSwitch tab, click the ID of the vSwitch that you associated with the route table in the vSwitch column. On the details page of the vSwitch, click the Route tab. In the Associated with Route Table section, you can view information about the custom route table that is associated with the vSwitch. View a custom route table