CIDR to IP range conversion using PowerShell

cidrToIpRange.ps1

# calculate IP address range from CIDR notation
# https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing

function cidrToIpRange {
    param (
        [string] $cidrNotation
    )

    $addr, $maskLength = $cidrNotation -split '/'
    [int]$maskLen = 0
    if (-not [int32]::TryParse($maskLength, [ref] $maskLen)) {
        throw "Cannot parse CIDR mask length string: '$maskLen'"
    }
    if (0 -gt $maskLen -or $maskLen -gt 32) {
        throw "CIDR mask length must be between 0 and 32"
    }
    $ipAddr = [Net.IPAddress]::Parse($addr)
    if ($ipAddr -eq $null) {
        throw "Cannot parse IP address: $addr"
    }
    if ($ipAddr.AddressFamily -ne [Net.Sockets.AddressFamily]::InterNetwork) {
        throw "Can only process CIDR for IPv4"
    }

    $shiftCnt = 32 - $maskLen
    $mask = -bnot ((1 -shl $shiftCnt) - 1)
    $ipNum = [Net.IPAddress]::NetworkToHostOrder([BitConverter]::ToInt32($ipAddr.GetAddressBytes(), 0))
    $ipStart = ($ipNum -band $mask) + 1
    $ipEnd = ($ipNum -bor (-bnot $mask)) - 1

    # return as tuple of strings:
    ([BitConverter]::GetBytes([Net.IPAddress]::HostToNetworkOrder($ipStart)) | ForEach-Object { $_ } ) -join '.'
    ([BitConverter]::GetBytes([Net.IPAddress]::HostToNetworkOrder($ipEnd)) | ForEach-Object { $_ } ) -join '.'
}

$start, $end = cidrToIpRange "192.168.100.14/24"
Write-Host "Start: $start, end: $end"

$start, $end = cidrToIpRange "10.77.1.1/18"
Write-Host "Start: $start, end: $end"