Powershell Script, Generate Active DHCP Leases

dhcp.ps1

# Define the DHCP Server and the list of Scope IDs (Zones)
$dhcpServer = "MYSERVER"  # Replace with the name or IP address of your DHCP server
$scopeIDs = @("10.2.0.0","10.3.0.0","192.168.0.0")  # Add all subnets here

# Import the DHCP Server Module (in case it's not loaded)
Import-Module DhcpServer

# Function to convert lease time to Linux format, handling null values
function Convert-LeaseTime($leaseTime) {
    if ($leaseTime -ne $null) {
        return $leaseTime.ToString("yyyy/MM/dd HH:mm:ss")
    } else {
        # Handle null by setting a default time or skipping
        return "2024/01/01 00:00:00"  # Default to Unix epoch time for null values
    }
}

# Output file for Linux DHCP leases
$outputFile = "C:\linux-dhcp-leases.txt"

# Clear the file if it exists, to avoid appending to old data
if (Test-Path $outputFile) {
    Remove-Item $outputFile
}

# Process each scope and fetch leases
foreach ($scopeID in $scopeIDs) {
    Write-Host "Processing leases for scope: $scopeID"

    # Get the list of active leases for the specified scope
    $leases = Get-DhcpServerv4Lease -ComputerName $dhcpServer -ScopeId $scopeID

    # Process each lease and convert it into the Linux DHCP lease format
    $leaseData = foreach ($lease in $leases) {
        $leaseStartTime = Convert-LeaseTime($lease.AddressStateTime)
        $leaseEndTime = Convert-LeaseTime($lease.LeaseExpiryTime)

        @"
lease $($lease.IPAddress) {
  starts $(($lease.AddressStateTime).DayOfWeek) $leaseStartTime;
  ends $(($lease.LeaseExpiryTime).DayOfWeek) $leaseEndTime;
  cltt $(($lease.AddressStateTime).DayOfWeek) $leaseStartTime;
  binding state active;
  next binding state free;
  hardware ethernet $($lease.ClientId);
  uid "$($lease.ClientId)";
  client-hostname "$($lease.HostName)";
}
"@
    }

    # Append the formatted data to the output file
    $leaseData | Out-File -FilePath $outputFile -Append
}

Write-Host "Leases have been exported to $outputFile in Linux-compatible format, including hostnames."