Work with route tables

Operations

• View a route table associated with a vSwitch
• Create a custom route table
• Modify the basic information about a route table
• Add and delete route entries
• Associate a route table with a vSwitch
• Disassociate a route table from a vSwitch
• Delete a custom route table

View a route table associated with a vSwitch

You can view the information about a route table that is associated with a vSwitch in the Virtual Private Cloud (VPC) console.

1. Log on to the VPC console.
2. In the left-side navigation pane, click vSwitch.
3. Select the region where the vSwitch is deployed.
4. On the vSwitch page, find the vSwitch that you want to manage and click its ID.
5. In the vSwitch Basic Information section, click the Route tab. In the Associated with Route Table section, you can view the ID and type of the associated route table.
   Route tables are classified into the following types:

   • System: The vSwitch is associated with a system route table. To associate the vSwitch with a custom route table, click Bind next to the system route table. In the Associate RouteTable dialog box, select the custom route table that you want to associate with the vSwitch.
   • Custom: The vSwitch is associated with a custom route table. To replace the custom route table, click Replace Associated Route Table and select another custom route table in the Associate RouteTable dialog box.

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.
   Click to view the regions that support custom route tables.

   Area	Region
   Asia Pacific	China (Qingdao), China (Beijing), China (Zhangjiakou), China (Hohhot), China (Ulanqab), China (Hangzhou), China (Shanghai), China (Heyuan), China (Shenzhen), China (Guangzhou), China (Chengdu), China (Hong Kong), Japan (Tokyo), Singapore (Singapore), Australia (Sydney), Malaysia (Kuala Lumpur), Indonesia (Jakarta), Philippines (Manila), India (Mumbai), and South Korea (Seoul)
   Europe & Americas	US (Silicon Valley), US (Virginia), Germany (Frankfurt), and UK (London)
   Middle East	UAE (Dubai)

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 custom route table belongs.
   VPC	Select the VPC to which the custom 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. For more information about how to upgrade an ECS instance, see Upgrade the instance types of subscription instances and Change the instance type of a pay-as-you-go instance. For more information about how to release an ECS instance, see Release an instance. 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 custom route table. The name must be 2 to 128 characters in length and can contain digits, underscores (_), and hyphens (-). It must start with a letter.
   Description	Enter a description for the custom route table. The description must be 2 to 256 characters in length. It 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. The 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

Modify the basic information about a route table

You can modify the name and description of a system route table or a 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 route table that you want to manage and click its ID.
5. On the details page of the route table, click Edit next to Name to modify the name of the route table.
   The name must be 2 to 128 characters in length and can contain letters, digits, underscores (_), and hyphens (-). The name must start with a letter.
6. Click Edit next to Description to modify the description of the route table.
   The description must be 2 to 256 characters in length. It cannot start with http:// or https://.

Add and delete route entries

• After you create a VPC, the system creates a system route table for the VPC and adds system route entries to the route table. The system route entries are used to route traffic within the VPC. You cannot create or delete system route entries. However, you can create custom route entries to route traffic from source CIDR blocks to specified destinations.
• Both system route tables and custom route tables allow you to add and delete custom route entries.

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 route table that you want to manage and click its ID.
5. On the details page of the route table, click the Route Entry List tab. On the Route Entry List tab, you can perform the following operations:
   • Add a custom route entry
     Click the Custom Route tab and then click Add Route Entry. In the Add Route Entry panel, set the following parameters and click OK.

     Parameter	Description
     Name	Enter a name for the custom 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 network traffic is forwarded. 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 CIDR blocks, 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, and IPv6 Gateway	After you specify the next hop type, select an instance from the drop-down list or create a new instance.

   • Delete a custom route entry
     1. Find the custom route entry that you want to delete and click Delete in the Actions column.
     2. In the Delete Route Entry message, click OK.

Associate a route table with a vSwitch

You can create a custom route table in a VPC and associate the route table with a vSwitch. This way, you can manage the routes of the vSwitch, which are called subnet routes. Subnet routes help you manage network traffic with more flexibility.

You can associate a route table with multiple vSwitches. Each vSwitch can be associated with only one system route table or one custom route table. After a custom route table is associated with a vSwitch, the system route table is automatically disassociated from the vSwitch.

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.

Disassociate a route table from a vSwitch

You can disassociate a custom route table from a vSwitch. After a custom route table is disassociated from a vSwitch, the vSwitch is automatically associated with the system 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, find the vSwitch that you want to disassociate and click Unbind in the Actions column.
6. In the Unbind Route Table message, click OK.
   After a custom route table is disassociated from a vSwitch, the vSwitch is automatically associated with the system route table.

Delete a custom route table

You can delete custom route tables. However, you cannot delete system route tables. If the custom route table that you want to delete is associated with a vSwitch, you must first disassociate the custom route table from the vSwitch.

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 route table that you want to delete and click Delete in the Actions column.
5. In the Delete Route Table message, click OK.

References

• DescribeRouteTableList: queries route tables.
• CreateRouteTable: creates a custom route table.
• ModifyRouteTableAttributes: modifies the name and description of a specified route table.
• CreateRouteEntry: creates a custom route entry.
• DeleteRouteEntry: deletes a custom route entry.
• AssociateRouteTable: associates a custom route table with a vSwitch in the same VPC.
• UnassociateRouteTable: disassociates a route table from a vSwitch.
• DeleteRouteTable: deletes a custom route table.