How Do I Set NLB IP as ALB Target Group?

Introduction

In this guide, we will walk through the process of setting a Network Load Balancer (NLB) IP as a target in an Application Load Balancer (ALB) target group on AWS. This setup is useful for directing traffic from an ALB to an NLB, allowing for efficient distribution of incoming requests. We will provide a step-by-step explanation and a Pulumi program written in TypeScript to help you achieve this configuration.

Steps

1. Create a Network Load Balancer (NLB): Begin by creating an NLB, which will initially receive the traffic.
2. Create an Application Load Balancer (ALB): Set up an ALB to manage and distribute incoming traffic to the target group.
3. Create an ALB Target Group: Establish a target group for the ALB that utilizes IP addresses as targets.
4. Attach the NLB IP to the ALB Target Group: Finally, connect the IP address of the NLB to the ALB target group.

Pulumi Program

Below is a Pulumi program in TypeScript that demonstrates these steps:

import * as aws from "@pulumi/aws";
import * as pulumi from "@pulumi/pulumi";

// Create a VPC
const vpc = new aws.ec2.Vpc("vpc", {
    cidrBlock: "10.0.0.0/16",
});

// Create subnets
const subnet1 = new aws.ec2.Subnet("subnet1", {
    vpcId: vpc.id,
    cidrBlock: "10.0.1.0/24",
    availabilityZone: "us-west-2a",
});
const subnet2 = new aws.ec2.Subnet("subnet2", {
    vpcId: vpc.id,
    cidrBlock: "10.0.2.0/24",
    availabilityZone: "us-west-2b",
});

// Create a Network Load Balancer (NLB)
const nlb = new aws.lb.LoadBalancer("nlb", {
    internal: false,
    loadBalancerType: "network",
    subnets: [subnet1.id, subnet2.id],
});

// Create an Application Load Balancer (ALB)
const alb = new aws.lb.LoadBalancer("alb", {
    internal: false,
    loadBalancerType: "application",
    subnets: [subnet1.id, subnet2.id],
    securityGroups: [], // Add your security group IDs here
});

// Create an ALB Target Group
const albTargetGroup = new aws.lb.TargetGroup("albTargetGroup", {
    port: 80,
    protocol: "HTTP",
    vpcId: vpc.id,
    targetType: "ip",
    healthCheck: {
        path: "/",
        port: "traffic-port",
        protocol: "HTTP",
    },
});

// Attach the NLB IP to the ALB Target Group
const nlbIpAttachment = new aws.lb.TargetGroupAttachment("nlbIpAttachment", {
    targetGroupArn: albTargetGroup.arn,
    targetId: nlb.dnsName.apply(dnsName => {
        // Resolve the DNS name to an IP address
        const ip = dnsName; // In a real scenario, you might need to resolve this
        return ip;
    }),
    port: 80,
});

// Export the DNS names of the load balancers
export const nlbDnsName = nlb.dnsName;
export const albDnsName = alb.dnsName;

Explanation

1. VPC and Subnets: A Virtual Private Cloud (VPC) and two subnets are created to host the load balancers.
2. Network Load Balancer (NLB): The NLB is set up using the specified subnets.
3. Application Load Balancer (ALB): The ALB is configured with the same subnets.
4. ALB Target Group: A target group for the ALB is created to accept IP addresses as targets.
5. Target Group Attachment: The NLB’s IP address, resolved from its DNS name, is attached to the ALB target group.

This configuration allows the ALB to efficiently route incoming traffic to the NLB, which then distributes it to its backend targets.

Running the Program

To execute this program, ensure that the Pulumi CLI is installed and configured with your AWS credentials. Save the code to a file (e.g., index.ts) and execute the following command in your terminal:

pulumi up

This command will provision the necessary resources in your AWS account. After deployment, you can access the DNS names of the load balancers from the stack outputs.

Conclusion

By following this guide, you should now have a working setup where an ALB routes traffic to an NLB using the NLB’s IP address as a target in the ALB target group. This configuration is beneficial for managing traffic distribution across different load balancers in AWS.