How can I ping computers on another network?

Question

I can successfully ping a computer on the same wireless network as me using the ping command in Terminal, however when I try to ping computers on outside wireless networks using their external IP address, it fails. How can I fix this or is there another way to do this?

Answer 1

Even if you can successfully ping another router on the internet - and this is often blocked - it only confirms the presence of this router, not of any computers behind it.

However many (but not all) routers will allow you to open ports from the outside to internal computers and this can provide a way to test that such computer is active - e.g. by installing and using nmap http://nmap.org/book/inst-macosx.html (for Windows you can use portqry.exe).

To find out how to open ports on the external router (i.e. the one which the computers on your 'outside wireless network' are using to access the network), you need to have administrator access to it, know the make and model and check how to set it either from its manual or, for many routers, http://portforward.com. Sorry I can't be more specific but it really depends on the router model...