Background

This section applies to the regions where you can visit the route table module directly from the navigation pane. Otherwise, refer to Route Table.

Route Table

A route table contains a set of rules, called routes, that are used to control where inbound and outbound subnet traffic is forwarded within a VPC. Each subnet in your VPC must be associated with a route table. A subnet can only be associated with one route table at a time, but you can associate multiple subnets with the same route table.

Default Route Table and Custom Route Table

When you create a VPC, the system automatically generates a default route table for the VPC. After a subnet is created, the subnet automatically associates with the default route table. You can add routes to, delete routes from, and modify routes in the default route table, but cannot delete the table. When you create a VPN, Cloud Connect, or Direct Connect connection, the default route table automatically delivers a route that cannot be deleted or modified. You can associate the subnet with the custom route table or replicate the route to the custom route table, and then add, modify, or delete the route in the custom route table.

You can use the default route table or create a custom route table for a subnet and then associate the custom route table with the subnet. You can delete the custom route table if it is no longer required.

• The custom route table associated with a subnet affects only the outbound traffic. The default route table determines the inbound traffic.
• To use a custom route table, you need to submit a service ticket. You need to click Increase quota on the Create Route Table page or choose More > Service Tickets > Create Service Ticket in the upper right corner of the page. For more information, see Submitting a Service Ticket.

For details about how to create a custom route table, see section Creating a Custom Route Table.

Route

A route, that is a routing rule, is configured with the destination, next hop type, and next hop to determine where the network traffic is directed. Routes are classified into system routes and custom routes.

• System route: Routes that are automatically added by the system and cannot be modified or deleted.
  After a route table is created, the system automatically adds the following system routes to the route table, so that instances in a VPC can communicate with each other.

  • Routes whose destination is 100.64.0.0/10 or 198.19.128.0/20.
  • Routes whose destination is a subnet CIDR block.
    

    In addition to the preceding system routes, the system automatically adds a route whose destination is 127.0.0.0/8, indicating the local loopback address.

• Custom route: A route that can be modified and deleted. The destination of a custom route cannot overlap with that of a system route.

  You can add a custom route and configure the destination, next hop type, and next hop in the route to determine where the network traffic is directed. Table 1 lists the supported types of next hops.

  Table 1 Next hop type

  Next Hop Type	Description
  ECS	Traffic intended for the destination is forwarded to an ECS in the VPC.
  Extension NIC	Traffic intended for the destination is forwarded to the extension NIC of an ECS in the VPC.
  VPN gateway	Traffic intended for the destination is forwarded to a VPN gateway.
  Cloud connection	Traffic intended for the destination is forwarded to a cloud connection.
  Direct Connect gateway	Traffic intended for the destination is forwarded to a Direct Connect gateway.
  NAT gateway	Traffic intended for the destination is forwarded to a NAT gateway.
  VPC peering connection	Traffic intended for the destination is forwarded to a VPC peering connection.
  Virtual IP address	Traffic intended for the destination is forwarded to a virtual IP address and then sent to active and standby ECSs to which the virtual IP address is bound.
  VPC endpoint	Traffic intended for the destination is forwarded to a VPC endpoint.
  Cloud container	Traffic intended for the destination is forwarded to a cloud container.

  

  • When you add a custom route to a default route table, the next hop type cannot be set to VPN gateway or Direct Connect gateway.
  • If you have to specify the destination when creating a service, a system route is delivered. If you do not need to specify a destination when creating a service, a custom route that can be modified or deleted is delivered automatically.

    For example, you do not need to specify a destination when creating a NAT gateway, the system automatically delivers a custom route that you can modify or delete. However, when you create a VPN gateway, you need to specify the remote subnet, that is, the destination of a route. In this case, the system delivers a system route. If the route destination can be modified on the Route Tables page, the destination will be inconsistent with that configured remote subnet. To modify the destination, you can go to the specific service page to modify the remote subnet, then the route destination will be changed accordingly.

Custom Route Table Configuration Process

Figure 2 shows the process of creating and configuring a custom route table.

Figure 2 Route table configuration process

1. For details about how to create a custom route table, see Creating a Custom Route Table.
2. For details about how to add a custom route, see Adding a Custom Route.
3. For details about how to associate a subnet with a route table, see Associating a Subnet with a Route Table. After the association, the routes in the route table control the routing for the subnet.

Notes and Constraints

• A maximum of 200 routes can be added to each route table.
• The default route table cannot be deleted.
• The system route cannot be modified or deleted.
• The routes delivered by the VPN, Cloud Connect, and Direct Connect services to the default route table cannot be modified or deleted.
• Routes with the next hop type of cloud containers cannot be modified, replicated, or deleted.
• The gateway VPC endpoint routes delivered by the VPC Endpoint service to the default route table cannot be modified, replicated, or deleted. In addition, a gateway VPC endpoint route in the custom route table cannot be modified or deleted.
• When you add a custom route to a default route table, the next hop type cannot be set to VPN gateway or Direct Connect gateway.