So, I'm trying to set up a server to only allow connections from within the company I work for. I give it two IP ranges to allow connections from, and hit apply. And then...
I get disconnected.
So it's down from the third floor to the lab in the basement, to discover that I had indeed mis-typed the IP range. Quickly correct it, check from another computer in the lab that it actually works, and then back up to the third floor.
D'oh.
At least I know the firewall works!