What must be configured on an Elastic Load Balancing load balancer to accept incoming traffic?

To enable an Elastic Load Balancer to accept incoming traffic, it is essential to configure a listener. A listener is a process that checks for connection requests from clients to the load balancer. It is configured with a protocol (such as HTTP or HTTPS) and a port number (such as port 80 for HTTP or port 443 for HTTPS). When the listener is set up, it listens for incoming requests and routes them to the appropriate backend resources, such as EC2 instances, based on the rules defined.

Without a listener, the load balancer cannot process any traffic, as there would be no defined protocol or port through which it can receive requests. The listener essentially acts as the front door for incoming traffic, ensuring that requests are directed correctly to the intended application or service.

In contrast, while network interfaces, IP addresses, and route tables may play roles in the broader network architecture and operation of resources within AWS, they are not specifically required for the load balancer to accept incoming requests. The presence of a listener is the key requirement for directing traffic through the Elastic Load Balancer.