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

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