Help Center/ Elastic Load Balance/ User Guide/ User Guide for Shared Load Balancers/ Listener/ Adding a UDP Listener
Updated on 2025-07-02 GMT+08:00
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Adding a UDP Listener

Scenarios

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 news.

Constraints

  • UDP listeners do not support fragmentation.
  • The UDP listener port cannot be 4789.
  • Any UDP packet larger than 1,500 bytes will be discarded. To avoid this, ensure that the MTU value of the network interface is not greater than 1,500 bytes and modify the configuration files of applications based on the MTU value.
  • If the listener protocol is UDP, the protocol of the backend server group is UDP by default and cannot be changed.

Procedure

  1. Go to the load balancer list page.
  2. On the displayed page, locate the load balancer and click its name.
  3. Under Listeners, click Add Listener. Configure the parameters based on Table 1.
    Table 1 Parameters for configuring a UDP listener

    Parameter

    Description

    Name

    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 (Optional)

    Description

    Provides supplementary information about the listener.

    You can enter a maximum of 255 characters.
  4. Click Next: Configure Request Routing Policy.
    1. You are advised to select an existing backend server group.
    2. You can also select 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 a 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.

  5. Click Next: Confirm.
  6. Confirm the configurations and click Submit.
Parent topic: Listener