ELB checks the health status of backend servers. When a backend server is declared unhealthy, ELB stops distributing inbound traffic to the backend server. Network traffic is distributed to other backend servers that work as expected.
ELB supports session persistence. After session persistence is enabled, ELB distributes requests from a client to the same backend server during a session.
ELB distributes inbound traffic to backend servers that are deployed in different zones. ELB supports cross-zone deployment in most regions. If the primary zone fails, network traffic is automatically distributed to the secondary zone to avoid service disruptions.
Load balancing provides Internet-facing and internal-facing ELB instances. To process network traffic in a virtual private cloud (VPC), you can create an internal-facing ELB instance. To process network traffic from the Internet, you can create an Internet-facing ELB instance.
By default, ELB stores health check logs that are generated in the last three days. After you enable Object Storage Service (OSS), ELB can store all health check logs in OSS. This allows you to troubleshoot the issues that cause health check failures.
ELB manages certificates for HTTPS in a centralized way. You do not need to upload certificates to backend servers. Requests are decrypted on ELB before the requests are sent to backend servers. This reduces the CPU load on backend servers.
You can configure domain name-based forwarding rules and URL-based forwarding rules for the Layer 7 listeners of ELB . Listeners distribute requests to different backend servers based on forwarding rules.