Listeners for your Network Load Balancers - Elastic Load Balancing

Listeners for your Network Load Balancers

Before you start using your Network Load Balancer, you must add one or more listeners. A listener is a process that checks for connection requests, using the protocol and port that you configure. The rules that you define for a listener determine how the load balancer routes requests to the targets in one or more target groups.

For more information, see Request routing in the Elastic Load Balancing User Guide.

Listener configuration

Listeners support the following protocols and ports:

  • Protocols: TCP, TLS, UDP, TCP_UDP

  • Ports: 1-65535

You can use a TLS listener to offload the work of encryption and decryption to your load balancer so that your applications can focus on their business logic. If the listener protocol is TLS, you must deploy exactly one SSL server certificate on the listener. For more information, see TLS listeners for your Network Load Balancer.

To support both TCP and UDP on the same port, create a TCP_UDP listener. The target groups for a TCP_UDP listener must use the TCP_UDP protocol.

You can use WebSockets with your listeners.

All network traffic sent to a configured listener is classified as intended traffic. Network traffic that does not match a configured listener is classified as unintended traffic. ICMP requests other than Type 3 are also considered unintended traffic. Network Load Balancers drop unintended traffic without forwarding it to any targets. TCP data packets sent to the listener port for a configured listeners that are not new connections or part of an active TCP connection are rejected with a TCP reset (RST).

Listener rules

When you create a listener, you specify a rule for routing requests. This rule forwards requests to the specified target group. To update this rule, see Update a listener for your Network Load Balancer.