Configure service load-balancer in Azure Operator Nexus Kubernetes service

In this article, you learn how to configure a service load balancer in a Nexus Kubernetes cluster. The load balancer allows external services to access the services running within the cluster. The focus of this guide is on the configuration aspects, providing examples to help you understand the process. By following this guide, you're able to effectively configure service load balancers in your Nexus Kubernetes cluster.

Prerequisites

Before proceeding with this how-to guide, it's recommended that you:

• Refer to the Nexus Kubernetes cluster quickStart guide for a comprehensive overview and steps involved.
• Ensure that you meet the outlined prerequisites to ensure smooth implementation of the guide.
• Knowledge of Kubernetes concepts, including deployments and services.
• Contact your network administrator to acquire an IP address range that can be used for the load-balancer IP pool.

Limitations

• IP pool configuration is immutable: Once set, it can't be modified in a Nexus Kubernetes cluster.
• IP pool names must start with a lowercase letter or a digit and end with a lowercase letter or digit.
• IP pool names shouldn't exceed 63 characters to avoid potential issues or restrictions.
• IP address pools shouldn't overlap with existing POD CIDR, Service CIDR, or CNI prefix to prevent conflicts and networking problems within the cluster.

Configuration options

Before configuring the IP address pool for the service load-balancer, it's important to understand the various configuration options available. These options allow you to define the behavior and parameters of the IP address pool according to your specific requirements.

Let's explore the configuration options for the IP address pool.

Required parameters

The IP address pool configuration requires the presence of two fields: addresses and name. These fields are essential for defining the IP address range and identifying the pool.

• The addresses field specifies the list of IP address ranges that can be used for allocation within the pool. You can define each range as a subnet in CIDR format. Avoid using a single IP address, such as /32 for IPv4 and /128 for IPv6.
• The name field serves as a unique identifier for the IP address pool. It helps associate the pool with a BGP (Border Gateway Protocol) advertisement, enabling effective communication within the cluster.

Optional parameters

In addition to the required fields, there are also optional fields available for further customization of the IP address pool configuration.

• The autoAssign field determines whether IP addresses are automatically assigned from the pool. This field is a string type with a default value of True. You can set it to either True or False based on your preference.
• The onlyUseHostIps field controls the use of IP addresses ending with .0 and .255 within the pool. Enabling this option restricts the usage to IP addresses between .1 and .254 (inclusive), excluding the reserved network and broadcast addresses.

Bicep template parameters for IP address pool configuration

The following JSON snippet shows the parameters required for configuring the IP address pool in the Bicep template.

"ipAddressPools": {
  "value": [
    {
      "addresses": ["<IP>/<CIDR>"],
      "name": "<pool-name>",
      "autoAssign": "True",  /* "True"/"False" */
      "onlyUseHostIps": "True"  /* "True"/"False" */
    }
  ]
}

To add the IP pool configuration to your cluster, you need to update the kubernetes-deploy-parameters.json file that you created during the quickStart. Include the IP pool configuration in this file according to your desired settings.

After adding the IP pool configuration to your parameter file, you can proceed with deploying the Bicep template. This action sets up your new cluster with the specified IP address pool configuration, allowing you to utilize the IP pool as intended.

By following these instructions, you can create a new Nexus Kubernetes cluster with the desired IP pool configuration and take advantage of the IP address pool for your cluster services.

Example parameters

This parameter file is intended to be used with the quickStart guide Bicep template for creating a cluster with BGP load balancer enabled. It contains the necessary configuration settings to set up the cluster with BGP load balancer functionality. By using this parameter file with the Bicep template, you can create a cluster with the desired BGP load balancer capabilities.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentParameters.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "kubernetesClusterName":{
      "value": "lb-test-cluster"
    },
    "adminGroupObjectIds": {
      "value": [
        "00000000-0000-0000-0000-000000000000"
      ]
    },
    "cniNetworkId": {
      "value": "/subscriptions/<subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.NetworkCloud/l3Networks/<l3Network-name>"
    },
    "cloudServicesNetworkId": {
      "value": "/subscriptions/<subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.NetworkCloud/cloudServicesNetworks/<csn-name>"
    },
    "extendedLocation": {
      "value": "/subscriptions/<subscription_id>/resourceGroups/<managed_resource_group>/providers/microsoft.extendedlocation/customlocations/<custom-location-name>"
    },
    "location": {
      "value": "eastus"
    },
    "sshPublicKeys": {
      "value": [
        {
          "keyData": "ssh-rsa AAAAB..."
        },
        {
          "keyData": "ssh-rsa AAAAC..."
        }
      ]
    },
    "ipAddressPools": {
      "value": [
        {
          "addresses": ["<IP>/<CIDR>"],
          "name": "<pool-name>",
          "autoAssign": "True",
          "onlyUseHostIps": "True"
        }
      ]
    }
  }
}

Example: Static IP address allocation for a service

To allocate a static IP address for a service, you can use the following commands.

Create a deployment

kubectl create deployment nginx --image=nginx --port 80

Static IP allocation (LoadBalancerIP)

kubectl expose deployment nginx \
    --name nginx-loadbalancer-pool1-static \
    --type LoadBalancer \
    --load-balancer-ip <IP from pool-1>

Replace <IP from pool-1> with the desired IP address from the IP pool.

Static IP allocation (ExternalIP)

kubectl expose deployment nginx \
    --name nginx-clusterip-pool1-static \
    --type ClusterIP \
    --external-ip <IP from pool-1>

Replace <IP from pool-1> with the desired IP address from the IP pool.

Example: IP address allocation for a service from specific IP pool

To allocate an IP address for a service from a specific IP pool, you can use the following command.

kubectl expose deployment nginx \
    --name nginx-loadbalancer-pool2-auto \
    --type LoadBalancer \
    --overrides '{"metadata":{"annotations":{"metallb.universe.tf/address-pool":"pool-2"}}}'

This command assigns an IP address to the service from the IP pool pool-2. Adjust the pool name as needed. Before trying out these examples, ensure that you have already created a Nexus Kubernetes cluster with two different IP address pools. If you haven't done so, follow the necessary steps to create the cluster and configure the IP pools accordingly.

Next steps

You can try deploying a network function (NF) within your Nexus Kubernetes cluster utilizing the newly configured load balancer. This configuration allows you to test the load balancing capabilities and observe how traffic is distributed among the instances of your NF.