Skip to content


Load Balancing

Load Balancing


A network load balancer (NLB) distributes IPv4 TCP/6443 traffic across a target group of controller nodes with a healthy kube-apiserver. Clusters with multiple controllers span zones in a region to tolerate zone outages.


A network load balancer (NLB) distributes IPv4 TCP/80 and TCP/443 traffic across two target groups of worker nodes with a healthy Ingress controller. Workers span the zones in a region to tolerate zone outages.

The AWS NLB has a DNS alias record (regional) resolving to 3 zonal IPv4 addresses. The alias record is output as ingress_dns_name for use in application DNS CNAME records. See Ingress on AWS.

TCP Services

Load balance TCP applications by adding a listener and target group. A listener and target group may map different ports (e.g 3333 external, 30333 internal).

# Forward TCP traffic to a target group
resource "aws_lb_listener" "some-app" {
  load_balancer_arn = module.tempest.nlb_id
  protocol          = "TCP"
  port              = "3333"

  default_action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.some-app.arn

# Target group of workers for some-app
resource "aws_lb_target_group" "some-app" {
  name        = "some-app"
  vpc_id      = module.tempest.vpc_id
  target_type = "instance"

  protocol = "TCP"
  port     = 3333

  health_check {
    protocol = "TCP"
    port     = 30333

Pass worker_target_groups to the cluster to register worker instances into custom target groups.

module "tempest" {
  worker_target_groups = [,


  • AWS NLBs and target groups do not support UDP
  • Global Accelerator does support UDP, but its expensive


Add firewall rules to the worker security group.

resource "aws_security_group_rule" "some-app" {
  security_group_id = module.tempest.worker_security_groups[0]

  type        = "ingress"
  protocol    = "tcp"
  from_port   = 3333
  to_port     = 30333
  cidr_blocks = [""]


Add a custom route to the VPC route table.

data "aws_route_table" "default" {
  vpc_id = module.temptest.vpc_id
  subnet_id = module.tempest.subnet_ids[0]

resource "aws_route" "peering" {
  route_table_id =
  destination_cidr_block = ""


IPv6 Feature Supported
Node IPv6 address Yes
Node Outbound IPv6 Yes
Kubernetes Ingress IPv6 Yes