Find all computers on a network – Using Nmap – free tool

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I’m a huge fan of a tool called nmap (nmap.org).  It is a network tool that can do many things.  The most simple is to determine if a host is active.  Anytime I connect to any network I run a quick scan to see who my neighbors are on the network.

To do a network scan with nmap you only need one bit of information. Your IP address.  Below is a scan from my local network.  I was able to do a quick ipconfig to see my local IP was (192.168.2.118) armed with that information I can tell that the network segment is 192.168.2.1/24.

To scan the network you only need to issue the command

nmap -sP 192.168.2.1/24

Here is the result on my windows machine.

The scan took 9.16 seconds.  This is a pretty fast network scan.  In 9 seconds I was able to determine I have 12 devices connected, a few iphones, ipad, printer, and other machines.

I am always interested in performance and I wanted to see if my linux machine would do the scan faster.  (NOTE:  the windows machine is using a 802.11 G network and the linux machine is over the LAN bridge using Wireless G as well)

The Linux results of the same nmap command ran in 5.4 Seconds.  In this simple test the linux nmap process was a bit faster.

 Overall it is always a great idea to see what and how is around you when on a network.  I did not go into more detail but you can always use nmap to do more investigation.   I can cover that in a later article.

Happy scanning.

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