Why is the ID for a subnet created using Azure Resource Manager Powershell cmdlets null? - azure

Question

I am trying to provision some network resources in Azure and I am running into a blocker with a step that tries to reference a previously created subnet's Id property.
Here's the command to retrieve the subnet details:
$gwsubnet = Get-AzureRmVirtualNetworkSubnetConfig -Name 'GatewaySubnet' -VirtualNetwork $vnet
And then outputting the value of $gwsubnet in the console:
Name : GatewaySubnet
Id :
Etag :
ProvisioningState :
AddressPrefix : 10.1.1.0/24
IpConfigurations : null
NetworkSecurityGroup : null
RouteTable : null
Note that the Id property is null. This causes an error for a future step, e.g.:
$gwipconfig = New-AzureRmVirtualNetworkGatewayIpConfig -Name config1 -SubnetId $gwsubnet.Id -PublicIpAddressId $gwpip.Id
Gives the following error:
New-AzureRmVirtualNetworkGatewayIpConfig : Cannot validate argument on parameter 'SubnetId'. The argument is null or empty. Supply an argument that is not null or empty and then try the
command again.
At line:1 char:99
+ ... nfig -SubnetId $gwsubnet.Id -PublicIpAddressId $gwpip.Id
+ ~~~~~~~~~~~~
+ CategoryInfo : InvalidData: (:) [New-AzureRmVirtualNetworkGatewayIpConfig], ParameterBindingValidationException
+ FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.Azure.Commands.Network.NewAzureVirtualNetworkGatewayIpConfigCommand
I'm struggling with how to have my subnet have an Id assigned to it. Is this something that I need to logout/login again to see? thanks for the help.

Answer 1

The problem you are having is that the subnet Id isn't created until you have created the virtual network.
When you run Get-AzureRmVirtualNetworkSubnetConfig all you create is a configuration to attach to New-AzureRmVirtualNetwork Once you have run that command it will connect to Azure, deploy the Vnet, create the subnet and at that state it will create a subnet Id.
The following code will show you what I mean...
$DNSNameLabel = "mydnsname"
$NetworkName = "MyNet"
$NICName = "MyNIC"
$PublicIPAddressName = "MyPIP"
$SubnetName = "MySubnet"
$SubnetAddressPrefix = "10.0.0.0/24"
$VnetAddressPrefix = "10.0.0.0/16"
$SingleSubnet = New-AzureRmVirtualNetworkSubnetConfig `
-Name $SubnetName `
-AddressPrefix $SubnetAddressPrefix
#At this point nothing is created, so there is no valid subnet id
$Vnet = New-AzureRmVirtualNetwork -Name $NetworkName `
-ResourceGroupName $ResourceGroupName `
-Location $LocationName `
-AddressPrefix $VnetAddressPrefix `
-Subnet $SingleSubnet
#vnet and subnet are created, both get an id and etag
$vnet = Get-AzureRmVirtualNetwork -Name $NetworkName
-ResourceGroupName $ResourceGroupName
$vnet.Subnets[0].Id
Which will give
/subscriptions/{Subscription ID}/resourceGroups/MyResourceGroup/providers/Microsoft.Network/virtualNetworks/MyNet/subnets/MySubnet