Load balancing on multiple IP configurations using PowerShell

This article describes how to use Azure Load Balancer with multiple IP addresses on a secondary network interface (NIC). For this scenario, we have two VMs running Windows, each with a primary and a secondary NIC. Each of the secondary NICs has two IP configurations. Each VM hosts both websites contoso.com and fabrikam.com. Each website is bound to one of the IP configurations on the secondary NIC. We use Azure Load Balancer to expose two frontend IP addresses, one for each website, to distribute traffic to the respective IP configuration for the website. This scenario uses the same port number across both frontends, as well as both backend pool IP addresses.

Steps to load balance on multiple IP configurations


We recommend that you use the Azure Az PowerShell module to interact with Azure. See Install Azure PowerShell to get started. To learn how to migrate to the Az PowerShell module, see Migrate Azure PowerShell from AzureRM to Az.

Follow the steps below to achieve the scenario outlined in this article:

  1. Install Azure PowerShell. See How to install and configure Azure PowerShell for information about installing the latest version of Azure PowerShell, selecting your subscription, and signing in to your account.

  2. Create a resource group using the following settings:

    $location = "westcentralus".
    $myResourceGroup = "contosofabrikam"

    For more information, see Step 2 of Create a Resource Group.

  3. Create an Availability Set to contain your VMs. For this scenario, use the following command:

    New-AzAvailabilitySet -ResourceGroupName "contosofabrikam" -Name "myAvailset" -Location "West Central US"
  4. Follow instructions steps 3 through 5 in Create a Windows VM article to prepare the creation of a VM with a single NIC. Execute step 6.1, and use the following instead of step 6.2:

    $availset = Get-AzAvailabilitySet -ResourceGroupName "contosofabrikam" -Name "myAvailset"
    New-AzVMConfig -VMName "VM1" -VMSize "Standard_DS1_v2" -AvailabilitySetId $availset.Id

    Then complete Create a Windows VM steps 6.3 through 6.8.

  5. Add a second IP configuration to each of the VMs. Follow the instructions in Assign multiple IP addresses to virtual machines article. Use the following configuration settings:

    $NicName = "VM1-NIC2"
    $RgName = "contosofabrikam"
    $NicLocation = "West Central US"
    $IPConfigName4 = "VM1-ipconfig2"
    $Subnet1 = Get-AzVirtualNetworkSubnetConfig -Name "mySubnet" -VirtualNetwork $myVnet

    You do not need to associate the secondary IP configurations with public IPs for the purpose of this tutorial. Edit the command to remove the public IP association part.

  6. Complete steps 4 through 6 of this article again for VM2. Be sure to replace the VM name to VM2 when doing this. Note that you do not need to create a virtual network for the second VM. You may or may not create a new subnet based on your use case.

  7. Create two public IP addresses and store them in the appropriate variables as shown:

    $publicIP1 = New-AzPublicIpAddress -Name PublicIp1 -ResourceGroupName contosofabrikam -Location 'West Central US' -AllocationMethod Dynamic -DomainNameLabel contoso
    $publicIP2 = New-AzPublicIpAddress -Name PublicIp2 -ResourceGroupName contosofabrikam -Location 'West Central US' -AllocationMethod Dynamic -DomainNameLabel fabrikam
    $publicIP1 = Get-AzPublicIpAddress -Name PublicIp1 -ResourceGroupName contosofabrikam
    $publicIP2 = Get-AzPublicIpAddress -Name PublicIp2 -ResourceGroupName contosofabrikam
  8. Create two frontend IP configurations:

    $frontendIP1 = New-AzLoadBalancerFrontendIpConfig -Name contosofe -PublicIpAddress $publicIP1
    $frontendIP2 = New-AzLoadBalancerFrontendIpConfig -Name fabrikamfe -PublicIpAddress $publicIP2
  9. Create your backend address pools, a probe, and your load balancing rules:

    $beaddresspool1 = New-AzLoadBalancerBackendAddressPoolConfig -Name contosopool
    $beaddresspool2 = New-AzLoadBalancerBackendAddressPoolConfig -Name fabrikampool
    $healthProbe = New-AzLoadBalancerProbeConfig -Name HTTP -RequestPath 'index.html' -Protocol http -Port 80 -IntervalInSeconds 15 -ProbeCount 2
    $lbrule1 = New-AzLoadBalancerRuleConfig -Name HTTPc -FrontendIpConfiguration $frontendIP1 -BackendAddressPool $beaddresspool1 -Probe $healthprobe -Protocol Tcp -FrontendPort 80 -BackendPort 80
    $lbrule2 = New-AzLoadBalancerRuleConfig -Name HTTPf -FrontendIpConfiguration $frontendIP2 -BackendAddressPool $beaddresspool2 -Probe $healthprobe -Protocol Tcp -FrontendPort 80 -BackendPort 80
  10. Once you have these resources created, create your load balancer:

    $mylb = New-AzLoadBalancer -ResourceGroupName contosofabrikam -Name mylb -Location 'West Central US' -FrontendIpConfiguration $frontendIP1 -LoadBalancingRule $lbrule -BackendAddressPool $beAddressPool -Probe $healthProbe
  11. Add the second backend address pool and frontend IP configuration to your newly created load balancer:

    $mylb = Get-AzLoadBalancer -Name "mylb" -ResourceGroupName $myResourceGroup | Add-AzLoadBalancerBackendAddressPoolConfig -Name fabrikampool | Set-AzLoadBalancer
    $mylb | Add-AzLoadBalancerFrontendIpConfig -Name fabrikamfe -PublicIpAddress $publicIP2 | Set-AzLoadBalancer
    Add-AzLoadBalancerRuleConfig -Name HTTP -LoadBalancer $mylb -FrontendIpConfiguration $frontendIP2 -BackendAddressPool $beaddresspool2 -Probe $healthProbe -Protocol Tcp -FrontendPort 80 -BackendPort 80 | Set-AzLoadBalancer
  12. The commands below get the NICs and then add both IP configurations of each secondary NIC to the backend address pool of the load balancer:

    $nic1 = Get-AzNetworkInterface -Name "VM1-NIC2" -ResourceGroupName "MyResourcegroup";
    $nic2 = Get-AzNetworkInterface -Name "VM2-NIC2" -ResourceGroupName "MyResourcegroup";
    $mylb = $mylb | Set-AzLoadBalancer
    $nic1 | Set-AzNetworkInterface
    $nic2 | Set-AzNetworkInterface
  13. Finally, you must configure DNS resource records to point to the respective frontend IP address of the Load Balancer. You may host your domains in Azure DNS. For more information about using Azure DNS with Load Balancer, see Using Azure DNS with other Azure services.

Next steps