<# 
=========================================================
   Windows Server 2025 – Optimized IP Scanner (PowerShell 7.4)
   Detect Used / Free IPs + Hostnames + MAC + RTT
   Author: ChatGPT
=========================================================
#>

param(
    [string]$Subnet = "192.168.1",
    [string]$OutputPath = "C:\IP_Scan_Report_2025.csv"
)

Write-Host "`nStarting IP scan on subnet $Subnet.0/24 ..." -ForegroundColor Cyan
$StartTime = Get-Date

# Enable fast parallel processing in PowerShell 7.4
$IPs = 1..254 | ForEach-Object { "$Subnet.$_" }

$Results = $IPs | ForEach-Object -Parallel {

    $ip = $_
    $used = Test-Connection -Count 1 -Quiet -TimeoutSeconds 1 $ip

    if ($used) {
        # Try DNS name resolution
        try {
            $hostname = [System.Net.Dns]::GetHostEntry($ip).HostName
        } catch {
            $hostname = "Unknown"
        }

        # Grab MAC address from ARP table
        $arpEntry = arp -a $ip | Select-String $ip
        if ($arpEntry) {
            $mac = ($arpEntry.ToString().Split(" ", [System.StringSplitOptions]::RemoveEmptyEntries))[1]
        } else {
            $mac = "Unknown"
        }

        # Measure RTT (ping response time)
        try {
            $rtt = (Test-Connection -Count 1 $ip).ResponseTime
        } catch {
            $rtt = 0
        }

        [PSCustomObject]@{
            IPAddress = $ip
            Status    = "Used"
            Hostname  = $hostname
            MAC       = $mac
            RTTms     = $rtt
            ScanTime  = (Get-Date)
        }

    }
    else {
        [PSCustomObject]@{
            IPAddress = $ip
            Status    = "Free"
            Hostname  = "-"
            MAC       = "-"
            RTTms     = "-"
            ScanTime  = (Get-Date)
        }
    }

} -ThrottleLimit 50  # Tuned for Server 2025 multi-core performance

# Output to screen in table format
$Results | Sort-Object IPAddress | Format-Table

# Export CSV
$Results | Sort-Object IPAddress | Export-Csv -NoTypeInformation -Path $OutputPath

# Export HTML as well
$Results | ConvertTo-Html | Out-File ($OutputPath.Replace(".csv", ".html"))

$EndTime = Get-Date
$Duration = $EndTime - $StartTime

Write-Host "`nScan complete!" -ForegroundColor Green
Write-Host "Results saved to: $OutputPath"
Write-Host "Total duration: $($Duration.TotalSeconds) seconds`n"