- ping- this tests whether a network card (on a PC, printer, server, anything !) is "responding" (generally, switched on). So typing "ping mypc.something.com" into a command line should get a response like "Reply from mypc.something.com: bytes=32 time<1ms TTL=128".
- ipconfig or ifconfig (depepnding on the OS)- just typing it in like this should give you basice network information like your IP address, gateway etc.
- tracert (traceroute)- this is a bit like ping, but tells you how your request gets to it’s destination- it doesn’t flag up network switches but will give you any routers that are between you and the machine you want to find out about:
1 3 ms 4 ms 4 ms router.1.com
2 1 ms <1 ms 1 ms router.2.com
3 2 ms 2 ms 2 ms router.3.com
4 16 ms 16 ms 18 ms router.4.com
5 216 ms 185 ms 256 ms router.5.com
6 169 ms 279 ms 388 ms router.6.com
These tools are handy for troubleshooting but they can’t guarantee to solve problems, because they rely on specific network ports that might get blocked by firewalls. So just because you get a "Request timed out" reply from a particular PC or server doesn’t mean it’s off- it might just have a firewall installed, and- for example- could be happily serving up web pages.