Okay guys, thanks. I've set the subnet mask to 255.255.255.0, and DHCP leases 16 to 150 (just to be safe). But now a bunch of the computers on the network can't get on the network. They're complaining about IP address conflicts. I've rebooted these computers, power cycles the router and all attached switches, but they're still giving me the problem. I've tried releasing and renewing the IP addresses, but that can't even get going...
Perhaps your network has more static IP addresses than you thought? If you have a machine with a IP address conflict, you can find the MAC address of the conflicting machine by (a) temporarily disconnecting the one reporting the conflict (b) running ping <conflicted-IP-address> on a separate machine (c) running "arp -a" on that separate machine. At least if it's Linux.
Of course, if the sysadmin's record-keeping isn't good enough to work out which MAC address corresponds to which machine, that doesn't help.
Rebooting the router, of course, causes it to forget which IP addresses it handed out to which MAC addresses, and start again from .16. If you're concerned that some hosts are keeping hold of IP addresses given by a previous incarnation of the router, change the DHCP range to a disjoint one (e.g. 150-250). That operation itself should not reboot the router. Then, once all the incorrect leases have expired (the default least time on a WRT54G is one day), you can change the DHCP range back to what you want it to be.
Peter
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