created PS_script which for know the free IP and CIDR in exacting Vnet in Azure but getting error

[mohammad96]

While executing the powershell script as per below script which i made for check avaiable IP and free CIDR in exacting Vnet in Azure but getting failed as per below error.

# Connect to your Azure account (if not already connected)
Connect-AzAccount -Subscription xyz-sub
# Define the Azure resource group and virtual network name
$resourceGroupName = "network-01-rg"
$virtualNetworkName = "network-01-vnet"

# Get the virtual network object
$virtualNetwork = Get-AzVirtualNetwork -ResourceGroupName $resourceGroupName -Name $virtualNetworkName

# Check if the virtual network exists
if (!$virtualNetwork) {
    Write-Host "Virtual network '$virtualNetworkName' not found in resource group '$resourceGroupName'."
    return
}

# Function to find a free IP CIDR range in a given subnet
function Get-FreeIPCIDRRange {
    param (
        [string]$subnetAddressPrefix,
        [array]$existingSubnets
    )
    $subnetCIDR = [System.Net.IPAddress]::Parse($subnetAddressPrefix).GetAddressBytes()
    $subnetBits = $subnetAddressPrefix.Split("/")[1]
    foreach ($existingSubnet in $existingSubnets) {
        $existingCIDR = [System.Net.IPAddress]::Parse($existingSubnet.AddressPrefix).GetAddressBytes()
        $existingBits = $existingSubnet.AddressPrefix.Split("/")[0]
        # Calculate the number of addresses in each subnet
        $totalAddresses = [System.Math]::Pow(2, 32 - $existingBits)
        # Calculate the first address of the existing subnet
        $existingStartAddress = $existingCIDR[0] -band ([System.Net.IPAddress]::Broadcast -bxor ([System.Math]::Pow(2, 32) - [System.Math]::Pow(2, 32 - $existingBits)))
        # Calculate the last address of the existing subnet
        $existingEndAddress = $existingStartAddress + $totalAddresses - 1
        # Calculate the first address of the new subnet
        $newStartAddress = $subnetCIDR[0] -band ([System.Net.IPAddress]::Broadcast -bxor ([System.Math]::Pow(2, 32) - [System.Math]::Pow(2, 32 - $subnetBits)))
        # If the new subnet's first address is greater than the existing subnet's last address, the range is free
        if ($newStartAddress -gt $existingEndAddress) {
            return $subnetAddressPrefix
        }
    }
    return $null
}
# Retrieve the existing subnets in the virtual network
$existingSubnets = $virtualNetwork.Subnets
# Find a free IP CIDR range for the new subnet
$availableCIDR = $null
for ($i = 32; $i -le 29; $i++) {
    $proposedCIDR = "172.28.$i.0/$i"
    $availableCIDR = Get-FreeIPCIDRRange -subnetAddressPrefix $proposedCIDR -existingSubnets $existingSubnets

    if ($availableCIDR -ne $null) {
        break
    }
}
# Check if a free IP CIDR range was found
if ($availableCIDR -ne $null) {
    Write-Host "A free IP CIDR range is available: $availableCIDR"
}
else {
    Write-Host "No free IP CIDR range is available in the virtual network '$virtualNetworkName'."
}

 Output Screenshot:-

What should i do changes in script so can get as an output with new free IP with CIDR range.

[#2]

my above question/script actually i want to know the free avaibale IP address with CIDR in exacting Vnet? (let say a new requiement are come in my project for create new subnet in exacting Vnet with 172.28.x.x/25 so these thing now we are doing with help of the attacged url link) and now i want to do automatically with help of script davidc.net/sites/default/subnets/subnets.html (using this url for deviding with one ip/cidr subnet to multiple ip/cider subnet –

Attached SS for reference.