two of the handiest things when setting up a network are ping and traceroute. The first lets you know that you have connectivity and the second lets you know how far you can go before running into problems, to help localize the fault. I had my old network firewall setup with pmfirewall and portsentry, so when someone tried to connect to a monitored port on my puter, it played a startrek wav file, ran traceroute on the offending ip and put it in a file on my desktop.