title: get full list of devices from arp -a command
body: <p>I made a (very) simple batch file:</p>
  
  <pre><code>@echo off
  :start
  arp -a | findstr 20-7c-8f-3f-03-9c
  cls
  if %errorlevel% GEQ 1 (
  echo The device is offline
  Echo Device is offline at %time% on %date%. &gt;&gt; log.txt
  ) else (
  echo The device is online.
  Echo Device is online at %time% on %date%. &gt;&gt; log.txt
  )
  timeout 3 &gt;nul /nobreak
  goto start
  </code></pre>
  
  <p>While this works fine and dandy, it doesn't work if said device is not listed, ie Phones. </p>
  
  <p>Here's what I mean.  </p>
  
  <p>All of the devices connected to my router don't show up in the <code>arp -a</code> output.   Say the Mac address of my ipod is <code>18:E7:F4:86:75:9F</code>.  Is there some alternative way to detect if it is on the LAN?  Or should I just other software.  I like using this, and having it always running in the background.  It would be an extremely useful tool.  I could tell when my parents get home, or just if anybody I know is at my house.  It would serve as a lazy security program.  Just thinking of some ideas and potential this could have.</p>
  
  <p>Am I just better off using Nmap?</p>