This script will return the assigned private ips of each machine in a given subnet. If no subnet is provided it will return the assigned private ips for every machine in all subnets with a configuration.

Get-AzureAssignedPrivateIpAddress.ps1

Param
(
	[Parameter(Mandatory=$true)]
	[string]$VirtualNetworkName,
	[Parameter(Mandatory=$false)]
	[string]$SubnetName = '',
	[Parameter(Mandatory=$true)]
	[string]$Location,
	[Parameter(Mandatory=$true)]
	[string]$ResourceGroupName
)
Begin
{
	$ResourceGroup = Get-AzureRmResourceGroup -Name $ResourceGroupName -Location $Location
	$VirtualNetwork =  Get-AzureRmVirtualNetwork -Name $VirtualNetworkName -ResourceGroupName $ResourceGroup.ResourceGroupName
	}
Process
{
	foreach ($SubnetConfig in (Get-AzureRmVirtualNetworkSubnetConfig -Name $SubnetName -VirtualNetwork $VirtualNetwork))
	{
		if ($SubnetConfig.IpConfigurations)
		{
			foreach ($IpConfiguration in $SubnetConfig.IpConfigurations)
			{
				if ($IpConfiguration.Id.Contains('loadBalancers'))
				{
					$LoadBalancer = Get-AzureRmLoadBalancer -Name $IpConfiguration.Id.Split('/')[8] -ResourceGroupName $IpConfiguration.Id.Split('/')[4]
					New-Object -TypeName psobject -Property @{
						Name = ($LoadBalancer.Name)
						Type = 'LoadBalancer'
						PrivateIpAddress = ($LoadBalancer.FrontendIpConfigurations |ForEach-Object {$_.PrivateIpAddress})
					}
				}
				else
				{
					$NetworkInterfaceName = $IpConfiguration.Id.Split('/')[8]
					$NetworkInterfaceResourceGroupName = $IpConfiguration.Id.Split('/')[4]
					$NetworkInterface =  Get-AzureRmNetworkInterface -Name $NetworkInterfaceName -ResourceGroupName $NetworkInterfaceResourceGroupName
					New-Object -TypeName psobject -Property @{
						Name = ($NetworkInterface.VirtualMachine.Id.Split('/')[8])
						Type = 'VirtualMachine'
						PrivateIpAddress = ($NetworkInterface.IpConfigurations |ForEach-Object {$_.PrivateIpAddress}) 
						}
					}
				}
			}
		else
		{
			}	
		}
	}
End
{
	}