Configure security groups for your Classic Load Balancer

When you use the AWS Management Console to create a load balancer, you can choose an existing security group or create a new one. If you choose an existing security group, it must allow traffic in both directions to the listener and health check ports for the load balancer. If you choose to create a security group, the console automatically adds rules to allow all traffic on these ports.

[Nondefault VPC] If you use the AWS CLI or API create a load balancer in a nondefault VPC, but you don't specify a security group, your load balancer is automatically associated with the default security group for the VPC.

[Default VPC] If you use the AWS CLI or API to create a load balancer in your default VPC, you can't choose an existing security group for your load balancer. Instead, Elastic Load Balancing provides a security group with rules to allow all traffic on the ports specified for the load balancer. Elastic Load Balancing creates only one such security group per AWS account, with a name of the form default_elb_id (for example, default_elb_fc5fbed3-0405-3b7d-a328-ea290EXAMPLE). Subsequent load balancers that you create in the default VPC also use this security group. Be sure to review the security group rules to ensure that they allow traffic on the listener and health check ports for the new load balancer. When you delete your load balancer, this security group is not deleted automatically.

If you add a listener to an existing load balancer, you must review your security groups to ensure they allow traffic on the new listener port in both directions.

Recommended rules for load balancer security groups

The security groups for your load balancers must allow them to communicate with your instances. The recommended rules depend on the type of load balancer, internet-facing or internal.

Internet-facing load balancer

The following table shows the recommended inbound rules for an internet-facing load balancer.

Source	Protocol	Port Range	Comment
0.0.0.0/0	TCP	listener	Allow all inbound traffic on the load balancer listener port

The following table shows the recommended outbound rules for an internet-facing load balancer.

Destination	Protocol	Port Range	Comment
instance security group	TCP	instance listener	Allow outbound traffic to instances on the instance listener port
instance security group	TCP	health check	Allow outbound traffic to instances on the health check port

Internal load balancers

The following table shows the recommended inbound rules for an internal load balancer.

Source	Protocol	Port Range	Comment
VPC CIDR	TCP	listener	Allow inbound traffic from the VPC CIDR on the load balancer listener port

The following table shows the recommended outbound rules for an internal load balancer.

Destination	Protocol	Port Range	Comment
instance security group	TCP	instance listener	Allow outbound traffic to instances on the instance listener port
instance security group	TCP	health check	Allow outbound traffic to instances on the health check port

Assign security groups using the console

Use the following procedure to change the security groups associated with your load balancer.

To update a security group assigned to your load balancer using the console

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

2. On the navigation pane, under Load Balancing, choose Load Balancers.

3. Choose the name of the load balancer to open its detail page.

4. On the Security tab, choose Edit.

5. On the Edit security groups page, Under Security groups, add or remove security groups as needed.

   You can add up to five security groups.

6. When you are finished, choose Save changes.

Assign security groups using the AWS CLI

Use the following apply-security-groups-to-load-balancer command to associate a security group with a load balancer. The specified security groups override the previously associated security groups.

aws elb apply-security-groups-to-load-balancer --load-balancer-name my-loadbalancer --security-groups sg-53fae93f

The following is an example response:

{
  "SecurityGroups": [
     "sg-53fae93f"
  ]
}