Finding All Hosts On the LAN From Linux / Windows Workstation

"You can use normal ping command and shell script loop statement to print the list of all LAN computers from a shell prompt."

$ for ip in $(seq 1 254); do ping -c 1 192.168.1.$ip>/dev/null; [ $? -eq 0 ] && echo "192.168.1.$ip UP" || : ; done

http://www.cyberciti.biz/faq/mapping-lan-with-linux-unix-ping-command/