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Create a MetalLB load balancer using Azure Arc and Azure CLI

  • Article

Applies to: Azure Stack HCI, version 23H2

The main purpose of a load balancer is to distribute traffic across multiple nodes in a Kubernetes cluster. This can help prevent downtime and improve overall performance of applications. AKS enabled by Azure Arc supports creating MetalLB load balancer instance on your Kubernetes cluster using the Arc Kubernetes Runtime k8s-extension.

Prerequisites

  • An Azure Arc enabled Kubernetes cluster with at least one Linux node. You can create a Kubernetes cluster on Azure Stack HCI 23H2 using the Azure CLI or the Azure portal. AKS on Azure Stack HCI 23H2 clusters are Arc enabled by default.
  • Make sure you have enough IP addresses for the load balancer. For AKS on Azure Stack HCI 23H2, ensure that the IP addresses reserved for the load balancer do not conflict with the IP addresses in Arc VM logical networks and control plane IPs. For more information about IP address planning and networking in Kubernetes, see Networking requirements for AKS on Azure Stack HCI 23H2.
  • This how-to guide assumes you understand how Metal LB works. For more information, see the overview for MetalLB in Arc Kubernetes clusters.

Install the Azure CLI extension

Run the following command to install the necessary Azure CLI extension:

az extension add -n k8s-runtime --upgrade

Enable MetalLB Arc extension

Configure the following variables before proceeding:

Parameter Description
$subId Azure subscription ID of your Kubernetes cluster.
$rgName Azure resource group of your Kubernetes cluster.
$clusterName The name of your Kubernetes cluster.

Option 1: Enable MetalLB Arc extension using az k8s-runtime load-balancer enable command

To enable the MetalLB Arc extension using the following command, you must have Graph permission Application.Read.All. You can check if you have this permission by logging into your Azure subscription, and running the following command:

`az ad sp list --filter "appId eq '087fca6e-4606-4d41-b3f6-5ebdf75b8b4c'" --output json`

If the command fails, contact your Azure tenant administrator to get Application.Read.All role.

If you do have the permission, you can use the az k8s-runtime load-balancer enable command to install the Arc extension and register the resource provider for your Kubernetes cluster. The --resource-uri parameter refers to the resource manager ID of your Kubernetes cluster.

az k8s-runtime load-balancer enable --resource-uri subscriptions/$subId/resourceGroups/$rgName/providers/Microsoft.Kubernetes/connectedClusters/$clusterName

Option 2: Enable MetalLB Arc Kubernetes extension using az k8s-extension add command

If you don't have Graph permission Application.Read.All, you can follow these steps:

  1. Register the Microsoft.KubernetesRuntime RP if you haven't already done so. Note that you only need to register once per Azure subscription. You can also register resource providers using the Azure portal. For more information about how to register resource providers and required permissions, see how to register a resource provider.
az provider register -n Microsoft.KubernetesRuntime

You can check if the resource provider has been registered successfully by running the following command.

az provider show -n Microsoft.KubernetesRuntime -o table

Expected output:

Namespace                    RegistrationPolicy    RegistrationState
---------------------------  --------------------  -------------------
Microsoft.KubernetesRuntime  RegistrationRequired  Registered
  1. To install the MetalLB Arc extension, obtain the AppID of the MetalLB extension resource provider, and then run the extension create command. You must run the following commands once per Arc Kubernetes cluster.

Obtain the Application ID of the Arc extension by running az ad sp list. In order to run the following command, you must be a user member of your Azure tenant. For more information about user and guest membership, see default user permissions in Microsoft Entra ID.

$objID = az ad sp list --filter "appId eq '087fca6e-4606-4d41-b3f6-5ebdf75b8b4c'" --query "[].id" --output tsv

Once you have the $objID, you can install the MetalLB Arc extension on your Kubernetes cluster. To run the below command, you need to have Kubernetes extension contributor role.

az k8s-extension create --cluster-name $clusterName -g $rgName --cluster-type connectedClusters --extension-type microsoft.arcnetworking --config k8sRuntimeFpaObjectId=$objID -n arcnetworking

Deploy MetalLB load balancer on your Kubernetes cluster

You can now create a load balancer for your Kubernetes cluster remotely by running the az k8s-runtime load-balancer create command. This command creates a custom resource of type IPAddressPool in the namespace kube-system.

Configure the following variables before proceeding:

Parameter Description
$lbName The name of your MetalLB load balancer instance.
$advertiseMode The mode for your MetalLB load balancer. Supported values are ARP, BGP, or Both.
$ipRange The IP range for the MetalLB load balancer in ARP or Both mode.

If the advertise mode is BGP or Both, it also creates a custom resource of kind BGPAdvertisement. If the advertise mode is ARP or Both, it also creates a custom resource of type L2Advertisement:

az k8s-runtime load-balancer create --load-balancer-name $lbName --resource-uri subscriptions/$subId/resourceGroups/$rgName/providers/Microsoft.Kubernetes/connectedClusters/$clusterName --addresses $ipRange --advertise-mode $advertiseMode

Create a BGP peer for your Kubernetes cluster

Create a BGP peer for your Kubernetes cluster remotely by running the az k8s-runtime bgp-peer create command. Note that the BGP peer is effective for all load balancers that have BGP or Both advertise mode. Creating BGP peers is mandatory if you're using the MetalLB load balancer in BGP or Both mode.

Configure the following variables before proceeding:

Parameter Description
$peerName The name of your BGP peer.
$myASN AS number to use for the local end of the session.
$peerASN AS number to expect from the remote end of the session.
$peerIP Address to dial when establishing the session. 
az k8s-runtime bgp-peer create --bgp-peer-name $peerName --resource-uri subscriptions/$subId/resourceGroups/$rgName/providers/Microsoft.Kubernetes/connectedClusters/$clusterName --my-asn $myASN --peer-asn $peerASN --peer-address $peerIP

Next steps