title: Faster host discovery with nmap?
body: <p>I need to launch a background network device discovery process from a script on a regular basis, and it needs to be fairly fast. Currently, I launch NMAP like this:</p>
  
  <pre><code>nmap -sP 192.168.1.0/24
  </code></pre>
  
  <p>(I just made up the IP address, you get the idea). Anyway, the above will do a ping sweep on that class C network. The problem is that this command usually takes 30-40 seconds to complete. I would like to be able to do this much faster.</p>
  
  <p>My objective is simply device/host discovery - I just want to know the IP addresses of any machines that are up on the given network. Once a scan of some sort is completed, I can use the ARP command to get the MAC addresses as well for the up machines.</p>
  
  <p>So is there a faster way of doing this in nmap, or in any other free tool? I know about fing (which is faster) but I cannot embed find in a commercial product without paying an enormous license fee. So if there is a faster way of doing this in nmap or in some other free tool, that would be great.</p>
  
  <p>The tool must run in the command line on Ubuntu Linux. I'm not interested in GUI tools or tools that only run on other OS's.</p>