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Elastic Load Balancing
Network Load Balancers

Network Load Balancers

A load balancer serves as the single point of contact for clients. Clients send requests to the load balancer, and the load balancer sends them to targets, such as EC2 instances, in one or more Availability Zones.

To configure your load balancer, you create target groups, and then register targets with your target groups. Your load balancer is most effective if you ensure that each enabled Availability Zone has at least one registered target. You also create listeners to check for connection requests from clients and route requests from clients to the targets in your target groups.

Connectivity to your load balancer is not supported over VPN connections or VPC peering connections.

Load Balancer State

A load balancer can be in one of the following states:

provisioning

The load balancer is being set up.

active

The load balancer is fully set up and ready to route traffic.

failed

The load balancer could not be set up.

Load Balancer Attributes

The following are the load balancer attributes:

deletion_protection.enabled

Indicates whether deletion protection is enabled.

Availability Zones

You enable one or more Availability Zones for your load balancer when you create it. You cannot enable or disable Availability Zones for a Network Load Balancer after you create it.

When you enable an Availability Zone, you specify one subnet from that Availability Zone. The subnet must have at least 8 available IP addresses. Elastic Load Balancing creates a load balancer node in the Availability Zone and a network interface for the subnet (the description starts with "ELB net" and includes the name of the load balancer). Each load balancer node in the Availability Zone uses this network interface to get a static IP address. Note that you can view this network interface but you cannot modify it.

When you create an Internet-facing load balancer, you can optionally associate one Elastic IP address per subnet. You cannot add or change Elastic IP addresses for your subnets after you create the load balancer.

Each load balancer node distributes traffic across the registered targets in its Availability Zone only. If you enable multiple Availability Zones for your load balancer, this increases the fault tolerance of your applications.

Deletion Protection

To prevent your load balancer from being deleted accidentally, you can enable deletion protection. By default, deletion protection is disabled for your load balancer.

If you enable deletion protection for your load balancer, you must disable it before you can delete the load balancer.

To enable deletion protection using the console

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, under LOAD BALANCING, choose Load Balancers.

  3. Select the load balancer.

  4. Choose Description, Edit attributes.

  5. On the Edit load balancer attributes page, select Enable delete protection and choose Save.

To disable deletion protection using the console

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, under LOAD BALANCING, choose Load Balancers.

  3. Select the load balancer.

  4. Choose Description, Edit attributes.

  5. On the Edit load balancer attributes page, clear Enable delete protection and choose Save.

To enable or disable deletion protection using the AWS CLI

Use the modify-load-balancer-attributes command.

Connection Idle Timeout

For each request that a client makes through a load balancer, the load balancer maintains two connections. A front-end connection is between a client and the load balancer, and a back-end connection is between the load balancer and a target. For each front-end connection, the load balancer manages an idle timeout that is triggered when no data is sent over the connection for a specified time period. If no data has been sent or received by the time that the idle timeout period elapses, the front-end connection is broken. If a client sends data after the idle timeout period has elapses, it receives a TCP RST packet to indicate that the connection is no longer valid.

Elastic Load Balancing sets the idle timeout value to 350 seconds. You cannot modify this value. Your targets can use TCP keepalive packets to reset the idle timeout.