PingScan.ps1

function Get-IPRangeFromCIDR {
    param(
        $Range
    )
    # Set up empty list to contain the calculated range
    $IPList = [System.Collections.Generic.list[object]]::new()

    # split out input to IP and CIDR and calculate the num,ber of addresses with the power of MATH
    $startIP, [int]$CIDR = $Range -split "/"
    $NumberOfAddresses = [Math]::Pow(2, (32 - $CIDR))

    # Get IP bytes, reverse it and convert bytes it to UInt32 for start and end addresses
    $StartIPBytes = ([ipaddress]$startIP).GetAddressBytes()
    [array]::Reverse($StartIPBytes)
    $StartIP = [BitConverter]::ToUInt32($StartIPBytes, 0)

    $EndIPBytes = [ipaddress]::Parse(($startIP) + ($NumberOfAddresses)).GetAddressBytes()
    [array]::Reverse($EndIPBytes)
    $EndIP = [BitConverter]::ToUInt32($EndIPBytes, 0)

    # Increase the start address int untill it equals the end INT parsing the IP to string and adding it to the list
    while ($startIP -lt $endIP) {
        $IPList.Add(([IPaddress]::Parse($startIP)).IPAddresstoString)
        $startIP++
    }
    return $IPlist
}

function Invoke-PingSweep {
    [CmdletBinding()]
    param(
        [ValidatePattern('^(?:\d{1,3}\.){3}\d{1,3}/(0[1-9]|[12][0-9]|3[0-2])$')]
        $CIDRRange
    )


    $allMachines = Get-IPRangeFromCIDR -Range $CIDRRange

    $Results = $allMachines | % {
        [pscustomObject]@{
            Name = $_
            DNS  = [system.net.Dns]::GetHostEntryAsync($_)
            Ping = (New-Object System.Net.NetworkInformation.Ping).SendPingAsync($_, 600)
        }

    }

    $HealthReport = $results | % {
        [pscustomObject]@{
            Name = $_.Name
            DNSName = $_.DNS.Result.HostName 
            IPAddress = $_.Ping.Result.Address.IPAddressToString
            Status = $(
                switch ($_.Ping.Result.Status) {
                    "Success"  {"Online"}
                    "TimedOut" {"Offline"}
                    default    {"Unknown"}
                }
            )
            LastSeen = $(
                switch ($_.Ping.Result.Status) {
                    "Success"  {(((Get-Date).AddHours(2)).ToString("MM.dd.yyy h:mm:ss tt"))}
                }
            )
        }
    }
    return $HealthReport | where {$_.status -ne "Offline"}
}

Write-Host "[$(get-date)] Started ping scan on $($env:CIDR)"
Invoke-PingSweep $env:CIDR
Write-Host "[$(get-date)] Finished ping scan on $($env:CIDR)"