How to create multiple Subnets in pre-existing Vnet Powershell

Question

I have the following code which works good for adding a few subnets but I would like for this script to leverage a CSV file to import from and add the subnets into a pre-existing Vnet?

$appssubnet = New-AzVirtualNetworkSubnetConfig -Name servers -AddressPrefix "172.16.1.0/24" -NetworkSecurityGroupId "/subscriptions/xxxxxxxxxx-xxxx-xxxx-xxxxx-xxxxxxxxxxxx/resourceGroups/powershell-grp/providers/Microsoft.Network/networkSecurityGroups/app-nsg1"`
-RouteTableId "/subscriptions/xxxxxxxxxx-xxxx-xxxx-xxxxx-xxxxxxxxxxxx/resourceGroups/powershell-grp/providers/Microsoft.Network/routeTables/powershell-rt"
$serversubnet = New-AzVirtualNetworkSubnetConfig -Name apps -AddressPrefix "172.16.2.0/24" -RouteTableId "/subscriptions/xxxxxxxxxx-xxxx-xxxx-xxxxx-xxxxxxxxxxxx/resourceGroups/powershell-grp/providers/Microsoft.Network/routeTables/powershell-rt"
$dmz = New-AzVirtualNetworkSubnetConfig -Name dmz -AddressPrefix "172.16.3.0/24"
$updatedvnet = New-AzVirtualNetwork -Name "testsubnet" -ResourceGroupName "powershell-grp" -Location "North Europe" -AddressPrefix "172.16.0.0/16" -Subnet $serversubnet, $dmz, $appssubnet -Force:$true
$updatedvnet | Set-AzVirtualNetwork

Answer 1

Hello @DeHaven Graham

Here is a code:

Import-Csv .\subnets.csv | ForEach-Object {  
      
    $appssubnet = New-AzVirtualNetworkSubnetConfig -Name servers -AddressPrefix $_.appssubnet -NetworkSecurityGroupId "/subscriptions/xxxxxxxxxx-xxxx-xxxx-xxxxx-   
    xxxxxxxxxxxx/resourceGroups/powershell-grp/providers/Microsoft.Network/networkSecurityGroups/app-nsg1"`  
    -RouteTableId "/subscriptions/xxxxxxxxxx-xxxx-xxxx-xxxxx-xxxxxxxxxxxx/resourceGroups/powershell-grp/providers/Microsoft.Network/routeTables/powershell-rt"  
    $serversubnet = New-AzVirtualNetworkSubnetConfig -Name apps -AddressPrefix $_.serversubnet -RouteTableId "/subscriptions/xxxxxxxxxx-xxxx-xxxx-xxxxx-   
    xxxxxxxxxxxx/resourceGroups/powershell-grp/providers/Microsoft.Network/routeTables/powershell-rt"  
    $dmz = New-AzVirtualNetworkSubnetConfig -Name dmz -AddressPrefix $_.dmz  
    $updatedvnet = New-AzVirtualNetwork -Name "testsubnet" -ResourceGroupName "powershell-grp" -Location "North Europe" -AddressPrefix $_.addressprefix -Subnet $serversubnet, $dmz,   
    $appssubnet -Force:$true  
    $updatedvnet | Set-AzVirtualNetwork  
}  

CSV:

Answer 2

Hello @DeHaven Graham ,

If I have understood the questions correctly you want to add multiple Subnets in pre-existing Vnet using a PowerShell script. You can try running below mentioned code.

Connect-AzAccount -Identity  
Set-AzContext -Subscription "<Sub_Id>"  
Import-Csv "<file path>\Book1.csv" |`  
    ForEach-Object {  
        $Name = $_.Subnet_Name  
        $Address = $_.Subnet_Address  
        $virtualNetwork= Get-AzVirtualNetwork -Name myVNet -ResourceGroupName <rg_name>  
        Add-AzVirtualNetworkSubnetConfig -Name $Name -AddressPrefix $Address -VirtualNetwork $virtualNetwork  
        $virtualNetwork | Set-AzVirtualNetwork  
          
    }  

Example csv. You can add the extra field as per your requirements

I tried it on my end to add subnets in myVnet virtual network.

Hope this helps! Please let me know if you have ny additional questions. Thank you!

Answer 3

Hi,

The best method for creating multiple subnets will be importing from csv file.
Copy all the subnets in to excel file and save it as csv(Comma-separated values).

Since you already have a VNET, before creating subnets first set the subscription in which VNET is created.

Set-AzContext -Subscription "XXXXXXXXXX"

then import the file,

Import-Csv -Path "C:\Documents and Settings\subnets"

then run the foreach loop,

ForEach-Object {
$Name = $_.Subnet_Name
$Address = $_.Subnet_Address
$virtualNetwork= Get-AzVirtualNetwork -Name myVNet -ResourceGroupName <rgname>
Add-AzVirtualNetworkSubnetConfig -Name $Name -AddressPrefix $Address -VirtualNetwork $virtualNetwork
$virtualNetwork | Set-AzVirtualNetwork

 }

Hope this will help you !!

---

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Answer 4

Same using hash-table

PS /home/gabor> [hashtable]$subnets = @{                                                                                 

"subnet1" = "10.1.1.0/24" 
"subnet2" = "10.1.2.0/24" 
"AzureBastion" = "10.1.30.0/27"
"GatewaySubnet" = "10.1.3.0/27"

}

PS /home/gabor> foreach ($subnet in $subnets.GetEnumerator()) {

$vnet = Get-AzVirtualNetwork -Name $vnetName -ResourceGroupName $rg
Add-AzVirtualNetworkSubnetConfig -Name $($subnet.Name) -AddressPrefix $($subnet.Value) -VirtualNetwork $vnet
$vnet | Set-AzVirtualNetwork

}

PS /home/gabor> Get-AzVirtualNetwork -Name $vnetName -ResourceGroupName $rg | Select-Object -Property Subnets

Subnets
-------
{AzureBastion, subnet1, GatewaySubnet, subnet2}