Scan IP addresses on LAN
A simple solution to scan your network is nmap. Avoid to use nmap in external networks, as it could be considered as an "attack".
To install nmap in Debian/Ubuntu
apt-get install nmap
For other distibutions see here.
nmap -sP 192.168.1.1-254
Starting Nmap 6.25 ( http://nmap.org ) at 2013-08-24 19:38 EEST Nmap scan report for 192.168.1.1 Host is up (0.0027s latency). Nmap scan report for medisign.lo (192.168.1.51) Host is up (0.000059s latency). Nmap scan report for 192.168.1.71 Host is up (0.0046s latency). Nmap done: 254 IP addresses (3 hosts up) scanned in 6.05 seconds
Hope to find it helpful. Your comments are welcomed!