Help Center/ Elastic Load Balance/ FAQs/ Listeners/ Why Can't I Select the Target Backend Server Group When Adding or Modifying a Listener?

Updated on 2025-05-09 GMT+08:00

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Why Can't I Select the Target Backend Server Group When Adding or Modifying a Listener?

The backend server group's protocol (backend protocol) you want to select is not supported by the listener protocol (frontend protocol). There are some constraints on the backend protocol when you associate a backend server group with a listener.

Dedicated Load Balancer

**Table 1** The frontend and backend protocol
Load Balancer Specification	Frontend Protocol	Backend Protocol
Network load balancing	TCP	TCP
Network load balancing	UDP	UDP QUIC
Network load balancing	TLS	TLS TCP
Application load balancing	HTTP	HTTP
Application load balancing	HTTPS	HTTP HTTPS gRPC
Application load balancing	QUIC	HTTP HTTPS

Shared Load Balancer

**Table 2** The frontend and backend protocol
Frontend Protocol	Backend Protocol
TCP	TCP
UDP	UDP
HTTP	HTTP
HTTPS	HTTP

Parent topic: Listeners

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