tracking network lossage

[Jamie Zawinski]

Fairly often, I get tossed out of my telnet sessions with "connect: Network
is unreachable."  Obviously something is wrong with a router somewhere :-)
My question is, how can I tell which one?  I would like to both verify that
the problem isn't one I can fix locally, and be able to tell the person
responsible that the problem exists.  I think there's a program called
"traceroute" or something like that that will show you what gateways are
used between point A and B; where can I find this?

Thanks for any advice,
				-- Jamie