Register targets with your target group
When your target is ready to handle requests, you register it with one or more target groups. The target type of the target group determines how you register targets. For example, you can register instance IDs, IP addresses, or an Application Load Balancer. Your Network Load Balancer starts routing requests to targets as soon as the registration process completes and the targets pass the initial health checks. It can take a few minutes for the registration process to complete and health checks to start. For more information, see Health checks for your target groups.
If demand on your currently registered targets increases, you can register additional targets in order to handle the demand. If demand on your registered targets decreases, you can deregister targets from your target group. It can take a few minutes for the deregistration process to complete and for the load balancer to stop routing requests to the target. If demand increases subsequently, you can register targets that you deregistered with the target group again. If you need to service a target, you can deregister it and then register it again when servicing is complete.
When you deregister a target, Elastic Load Balancing waits until in-flight requests have completed.
This is known as connection draining. The status of a target is
draining
while connection draining is in progress. After deregistration
is complete, status of the target changes to unused
. For more information,
see Deregistration delay.
If you are registering targets by instance ID, you can use your load balancer with an Auto Scaling group. After you attach a target group to an Auto Scaling group and the group scales out, the instances launched by the Auto Scaling group are automatically registered with the target group. If you detach the load balancer from the Auto Scaling group, the instances are automatically deregistered from the target group. For more information, see Attaching a load balancer to your Auto Scaling group in the Amazon EC2 Auto Scaling User Guide.
Target security groups
When you register EC2 instances as targets, you must ensure that the security groups for these instances allow traffic on both the listener port and the health check port.
Considerations
-
Network Load Balancers do not have associated security groups. Therefore, the security groups for your targets must use IP addresses to allow traffic.
-
You can't use the security groups for the clients as a source in the security groups for the targets. Therefore, the security groups for your targets must use the IP addresses of the clients to allow traffic.
Recommended rules with client IP preservation enabled
The following are the recommended rules for the security groups for your targets with client IP preservation enabled.
Inbound rules | |||
---|---|---|---|
Source | Protocol | Port Range | Comment |
Client CIDR |
target |
target |
Allow traffic from your application, your network, or the internet |
VPC CIDR |
health check |
health check |
Allow health check traffic from the load balancer |
Recommended rules with client IP preservation disabled
The following are the recommended rules for the security groups for your targets with client IP preservation disabled.
Inbound rules | |||
---|---|---|---|
Source | Protocol | Port Range | Comment |
VPC CIDR
|
target |
target |
Allow traffic from the load balancer VPC † |
VPC CIDR |
health check |
health check |
Allow health check traffic from the load balancer |
† If you register targets by IP address but do not want to grant access to the entire VPC CIDR, you can grant access to the private IP addresses used by the load balancer nodes. There is one IP address per load balancer subnet. To find these addresses, use the following procedure.
To find the private IP addresses to allow
-
Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/
. -
In the navigation pane, choose Network Interfaces.
-
In the search field, enter the name of your Network Load Balancer. There is one network interface per load balancer subnet.
-
On the Details tab for each network interface, copy the address from Primary private IPv4 IP.
Network ACLs
When you register EC2 instances as targets, you must ensure that the network ACLs for the subnets for your instances allow traffic on both the listener port and the health check port. The default network access control list (ACL) for a VPC allows all inbound and outbound traffic. If you create custom network ACLs, verify that they allow the appropriate traffic.
The network ACLs associated with the subnets for your instances must allow the following traffic for an internet-facing load balancer.
Inbound | |||
---|---|---|---|
Source | Protocol | Port Range | Comment |
Client IP addresses |
listener |
listener |
Allow client traffic (instance target type) |
VPC CIDR |
listener |
listener |
Allow client traffic (ip target type) |
VPC CIDR |
health check |
health check |
Allow health check traffic from the load balancer |
Outbound | |||
Destination | Protocol | Port Range | Comment |
Client IP addresses |
listener |
listener |
Allow responses to clients (instance target
type) |
VPC CIDR |
listener |
listener |
Allow responses to clients (ip target type) |
VPC CIDR |
health check |
1024-65535 | Allow health check traffic |
The network ACLs associated with the subnets for your load balancer must allow the following traffic for an internet-facing load balancer.
Inbound | |||
---|---|---|---|
Source | Protocol | Port Range | Comment |
Client IP addresses |
listener |
listener |
Allow client traffic (instance target type) |
VPC CIDR |
listener |
listener |
Allow client traffic (ip target type) |
VPC CIDR |
health check |
1024-65535 | Allow health check traffic |
Outbound | |||
Destination | Protocol | Port Range | Comment |
Client IP addresses |
listener |
listener |
Allow responses to clients (instance target
type) |
VPC CIDR |
listener |
listener |
Allow responses to clients (ip target type) |
VPC CIDR |
health check |
health check |
Allow health check traffic |
VPC CIDR |
health check |
1024-65535 | Allow health check traffic |
For an internal load balancer, the network ACLs for the subnets for your instances and load balancer nodes must allow both inbound and outbound traffic to and from the VPC CIDR, on the listener port and ephemeral ports.
Register or deregister targets
Each target group must have at least one registered target in each Availability Zone that is enabled for the load balancer.
The target type of your target group determines how you register targets with that target group. For more information, see Target type.
Requirements and considerations
-
You can't register instances by instance ID if they use one of the following instance types: C1, CC1, CC2, CG1, CG2, CR1, G1, G2, HI1, HS1, M1, M2, M3, or T1.
-
You can't register instances by instance ID if they are in a VPC that is peered to the load balancer VPC (same Region or different Region). You can register these instances by IP address.
-
If you register a target by IP address and the IP address is in the same VPC as the load balancer, the load balancer verifies that it is from a subnet that it can reach.
-
For UDP and TCP_UDP target groups, do not register instances by IP address if they reside outside of the load balancer VPC or if they use one of the following instance types: C1, CC1, CC2, CG1, CG2, CR1, G1, G2, HI1, HS1, M1, M2, M3, or T1. Targets that reside outside the load balancer VPC or use an unsupported instance type might be able to receive traffic from the load balancer but then be unable to respond.
Contents
Register or deregister targets by instance ID
An instance must be in the running
state when you register
it.
Register or deregister targets by IP address
IPv4 targets
An IP address that you register must be from one of the following CIDR blocks:
-
The subnets of the VPC for the target group
-
10.0.0.0/8 (RFC 1918)
-
100.64.0.0/10 (RFC 6598)
-
172.16.0.0/12 (RFC 1918)
-
192.168.0.0/16 (RFC 1918)
The IP address type can't be changed after the target group is created.
When launching a Network Load Balancer in a shared Amazon VPC as a participant, you can only register targets in subnets that have been shared with you.
IPv6 targets
-
The IP addresses that you register must be within the VPC CIDR block or within a peered VPC CIDR block.
-
The IP address type can't be changed after the target group is created.
-
You can associate IPv6 target groups only to a dualstack load balancer with TCP or a TLS listeners.
Register or deregister targets using the AWS CLI
Use the register-targets command to add targets and the deregister-targets command to remove targets.