Updated on 2024-06-20 GMT+08:00

Adding a UDP Listener


You can add a UDP listener, if quick response is required but low reliability is acceptable. UDP listeners are suitable for scenarios such as video chat, gaming, and real-time financial quotations.


  • UDP listeners do not support fragmentation.
  • The port of UDP listeners cannot be 4789.
  • UDP packets can have any size less than 1,500 bytes. The packets will be discarded if they are bigger than 1,500 bytes. To avoid this, you need to modify the configuration files of the applications based on the maximum transmission unit (MTU) value.
  • If the listener protocol is UDP, the protocol of the backend server group is UDP by default and cannot be changed.


  1. Log in to the management console.
  2. In the upper left corner of the page, click and select the desired region and project.
  3. Click in the upper left corner to display Service List and choose Networking > Elastic Load Balance.
  4. On the Load Balancers page, locate the load balancer and click its name.
  5. Under Listeners, click Add Listener. Configure the parameters based on Table 1.
    Table 1 Parameters for configuring a UDP listener




    Specifies the listener name.

    Frontend Protocol

    Specifies the protocol that will be used by the load balancer to receive requests from clients.

    Select UDP.

    Frontend Port

    Specifies the port that will be used by the load balancer to receive requests from clients.

    The port number ranges from 1 to 65535.

    Access Control

    Specifies how access to the listener is controlled. For details, see What Is Access Control? The following options are available:

    • All IP addresses
    • Blacklist
    • Whitelist

    IP Address Group

    Specifies the IP address group associated with a whitelist or blacklist. If there is no IP address group, create one first. For more information, see IP Address Group.

    Transfer Client IP Address

    Specifies whether to transmit IP addresses of the clients to backend servers.

    Advanced Settings


    Provides supplementary information about the listener.

    You can enter a maximum of 255 characters.

  6. Click Next: Configure Request Routing Policy.
    1. You are advised to select an existing backend server group.
    2. You can also click Create new to create a backend server group.
      1. Configure the backend server group based on Table 2.
      2. Click Next: Add Backend Server. Add backend servers and configure health check for the backend server group.

        For details about how to add backend servers, see Backend Server Overview. For the parameters required for configuring a health check, see Table 3.

  7. Click Next: Confirm.
  8. Confirm the configurations and click Submit.