Get-Ipv4SubnetInfo.ps1

function Get-Ipv4SubnetInfo {
    <#
        .SYNOPSIS
            Get subnet information.
        .DESCRIPTION
            This function will return basic subnet information if given an IP address as well as either
            a subnet mask, or a mask length.
        .EXAMPLE
            Get-Ipv4SubnetInfo -IPAddress '10.10.10.1' -SubnetMask '255.255.0.0'
        .EXAMPLE
            Get-Ipv4SubnetInfo -IPAddress '192.168.0.4' -MaskLength 16
        .NOTES
            Author: Øyvind Kallstad
            Date: 28.04.2015
            Version: 1.0
    #>
    [CmdletBinding(DefaultParameterSetName = 'SubnetMask')]
    param (
        [Parameter()]
        [IPAddress] $IPAddress = ([System.Net.NetworkInformation.NetworkInterface]::GetAllNetworkInterfaces() | Where-Object {$_.OperationalStatus -eq 'Up' -and $_.NetworkInterfaceType -ne [System.Net.NetworkInformation.NetworkInterfaceType]::Loopback}).GetIPProperties().UnicastAddresses.Address.ToString(),

        [Parameter(ParameterSetName = 'SubnetMask')]
        [IPAddress] $SubnetMask = ([System.Net.NetworkInformation.NetworkInterface]::GetAllNetworkInterfaces() | Where-Object {$_.OperationalStatus -eq 'Up' -and $_.NetworkInterfaceType -ne [System.Net.NetworkInformation.NetworkInterfaceType]::Loopback}).GetIPProperties().UnicastAddresses.IPv4Mask,

        [Parameter(ParameterSetName = 'MaskLength')]
        [ValidateRange(0,32)]
        [int] $MaskLength
    )

    function ConvertTo-IPAddressUInt32 {
        param (
            [Parameter()]
            [ValidateNotNullOrEmpty()]
            [string] $IPAddress
        )

        try {
            $ip = [IPAddress]::Parse($IPAddress)
            $ipBytes = $ip.GetAddressBytes()
            [System.Array]::Reverse($ipBytes)
            $output = [BitConverter]::ToUInt32($ipBytes,0)
        }

        catch {
            Write-Warning $_.Exception.Message
        }

        Write-Output $output
    }
    function ConvertTo-IPAddress {
        param (
            [Parameter()]
            [ValidateRange([System.UInt32]::MinValue, [System.UInt32]::MaxValue)]
            [uint32] $IPAddress
        )

        try {
            $ipBytes = [BitConverter]::GetBytes($IPAddress)
            [System.Array]::Reverse($ipBytes)
        }

        catch {
            Write-Warning $_.Exception.Message
        }

        Write-Output ([IPAddress]$ipBytes)
    }
    function Get-IPv4AddressClass {
        [CmdletBinding()]
        param (
            [Parameter(Position = 0)]
            [IPAddress] $IPAddress
        )

        $ipBinary = ($IPAddress.GetAddressBytes() | ForEach-Object {[Convert]::ToString($_,2).PadLeft(8, '0') }) -join ''

        switch -Regex ($ipBinary) {
            '^1111' {$class = 'E';break}
            '^1110' {$class = 'D';break}
            '^110'  {$class = 'C';break}
            '^10'   {$class = 'B';break}
            '^0'    {$class = 'A';break}
        }

        Write-Output $class
    }
    function Test-Ipv4IsPrivate {
        [CmdletBinding()]
        param (
            [Parameter(Position = 0)]
            [IPAddress] $IPAddress
        )
        $private = $false
        $ipBinary = ($IPAddress.GetAddressBytes() | ForEach-Object {[Convert]::ToString($_,2).PadLeft(8, '0') }) -join ''
        if (($ipBinary -match '^1100000010101000') -or ($ipBinary -match '^101011000001') -or ($ipBinary -match '^0000101')) {
            $private = $true
        }
        Write-Output $private
    }

    if ($PSCmdlet.ParameterSetName -eq 'SubnetMask') {
        # convert the subnetmask to uint32
        $smUint32 = ConvertTo-IPAddressUInt32 -IPAddress $SubnetMask
        
        # calculate mask length (CIDR) by converting the subnetmask to binary and counting the 1s
        $SubnetMask.GetAddressBytes() | ForEach-Object {$cidr += [Convert]::ToString($_,2)}
        $MaskLength = $cidr.TrimEnd('0').Length
    }

    else {
        # create the subnetmask from the mask length, and convert to uint32
        $smUint32 = [Convert]::ToUInt32($(('1' * $MaskLength).PadRight(32, '0')), 2)
        $SubnetMask = ConvertTo-IPAddress -IPAddress $smUint32
    }

    # convert the IP address
    $ipUint32 = ConvertTo-IPAddressUInt32 -IPAddress $IPAddress
    
    # calculate the network and broadcast addresses of the subnet
    $networkAddress = $ipUint32 -band $smUint32
    $broadcastAddress = $ipUint32 -bor ((-bnot $smUint32) -band [UInt32]::MaxValue)

    # calculate the first and the last address in the subnet
    $firstIP = $networkAddress + 1
    $lastIP = $broadcastAddress - 1
    $usableAddresses = $lastIP - $networkAddress

    Write-Output ([PSCustomObject] [Ordered] @{
        NetworkAddress = (ConvertTo-IPAddress -IPAddress $networkAddress)
        SubnetMask = $SubnetMask
        FirstAddress = (ConvertTo-IPAddress -IPAddress $firstIP)
        LastAddress = (ConvertTo-IPAddress -IPAddress $lastIP)
        BroadcastAddress = (ConvertTo-IPAddress -IPAddress $broadcastAddress)
        UsableAddresses = $usableAddresses
        MaskLength = $MaskLength
        AddressClass = (Get-IPv4AddressClass -IPAddress $IPAddress)
        IsPrivate = (Test-Ipv4IsPrivate -IPAddress $IPAddress)
    })
}