To find all pingable hosts on the newtwork you are currently on first find your own ip. In Linux/OSX you can run the command ifconfig (windows uses the ‘ipconfig’ command):
malen@LKGADEFB8:~$ sudo ifconfig
eth0 Link encap:Ethernet HWaddr 00:1d:7e:ad:ef:b8
inet addr:192.168.0.77 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::21d:7eff:fead:efb8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:23647854 errors:0 dropped:83 overruns:0 frame:0
TX packets:31522391 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:320343317 (305.5 MiB) TX bytes:3340057852 (3.1 GiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:1736 errors:0 dropped:0 overruns:0 frame:0
TX packets:1736 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:159128 (155.3 KiB) TX bytes:159128 (155.3 KiB)
You here see your IP at ‘inet addr’ on eth0: 192.168.0.77. To see if there are any other hosts on the 192.168.0.x net use:
nmap -v -sP 192.168.0.1/24
This will ping all hosts on 192.168.0.x and show your result in a list
Host 192.168.0.1 appears to be down.
Host 192.168.0.2 appears to be down.
Host 192.168.0.3 appears to be down.
Host 192.168.0.4 appears to be down.
Host 192.168.0.5 appears to be down.
...
Host Slug (192.168.0.77) appears to be up.
...
Host 192.168.0.250 appears to be down.
Host 192.168.0.251 appears to be down.
Host 192.168.0.252 appears to be down.
Host 192.168.0.253 appears to be down.
Host 192.168.0.254 appears to be down.
Host 192.168.0.255 appears to be down.
Tested on OSX 10.7.4 and Debian Lenny