There are many terminal commands that allow to find all active IP addresses in a local network. In this article, I will show you a command that I think is simple and practical. This command uses the nmapcommand line utility to run.

Get Started

First of all, install the nmap command line utility by running this command via the terminal (Applications>> Accessories >> Terminal):

sudo apt-get install nmap

To find all active IP addresses in a local network, simply issue this command:

nmap -sP 192.168.0.*

This command has also the same function:

nmap -sP 192.168.0.0/24 

Note: This tutorial is tested under Ubuntu 10.10

ref : http://www.spotht.com/2010/11/scan-for-all-active-ip-addresses-in.html