I haven't had much success googling, because I'm not sure how to phrase the question. I don't know too much about networking (book recommendations welcome!).

I have a network with some headless RHEL 5 boxes. I don't know their IP addresses, but I need to ssh in. Is there a program that scans the network for machines, and returns something like hostnames and ip addresses? Or how would I gather that kind of information? I always see "UP BROADCAST RUNNING MULTICAST" when I type "ifconfig eth0", so it sounds possible.

In the meantime I can, of course, hook up a monitor and keyboard to find out, but it gets tedious with several machines and a test network that changes their IP addresses regularly.

You might try nmap. I've only used it to check firewall settings on my machine (i.e. port scanning). But the link has sections on host discovery and OS detection that look promising.

Aha! Looks cool. Thanks!

"nmap -sP 192.168.0.0/16" gives me the info I need.

Of course nmap is cool. it's the tool Trinity used when hacking in The Matrix Reloaded !!

http://insecure.org/