Help Center/ Elastic Load Balance/ Drawer/ Buying a Load Balancer/ Subnets/ Subnets (Dedicated Load Balancers)
Updated on 2025-07-25 GMT+08:00
Share

Subnets (Dedicated Load Balancers)

Frontend Subnet

The frontend subnet is the subnet where a load balancer is deployed.

The system assigns IP addresses in this subnet to load balancers for receiving requests based on the configured network type.

  • IPv4 private network: IPv4 private addresses will be assigned.
  • IPv6 network: IPv6 private or public addresses will be assigned.
  • If you select IPv6 network for Network Type and the selected VPC does not have any subnet that supports IPv6, enable IPv6 for at least one subnet or create a subnet that supports IPv6. For details, see the Virtual Private Cloud User Guide.
  • If you do not enable IPv6 for the specified backend subnet when you create a dedicated load balancer, the load balancer cannot use IPv6 addresses to route requests.

Backend Subnet

Load balancers use the IP addresses in the backend subnet to forward requests to the backend servers. You can see how many IP addresses are actually required on the console.

You can also call APIs to calculate the number of required IP addresses by referring to Elastic Load Balance API Reference.

By default, Subnet of the load balancer is selected. If the frontend subnet does not meet your network requirements, you can click the drop-down menu to select another subnet in the same VPC or add a new subnet.

FAQ

Can I Change the VPC and Subnet for My Load Balancer?

You cannot change the VPC and subnet for your shared load balancers, but you can change the subnet for your dedicated load balancers.

  • After a load balancer is created, do not change the backend subnet.
    • If the subnet is changed, the IP addresses used by the load balancer will not be released, and traffic from the previous backend subnet is still need to be allowed to backend servers.
    • Traffic from the new backend subnet also needs to be allowed to backend servers.

Why Multiple IP Addresses Are Required When I Create a Dedicated Load Balancer?

Dedicated load balancers use IP addresses in the backend subnet for internal communications.

Generally, two IP addresses are required for creating a dedicated load balancer in a single AZ, and six IP addresses are required for creating a dedicated load balancer with IP as a backend enabled. If you create a dedicated load balancer in multiple AZs, more IP addresses will be required. There is an algorithm to determine how many IP addresses are required.

Parent Topic: Subnets