I have a home network, with an OpenWrt router operating successfully as DHCP server (using DNSMasq). I'm planning to install LinuxMCE on my main fileserver and in order for this to properly detect devices around the home it requires that it is the DHCP server. That would be fine except that I sometimes power down the fileserver (eg. when my in-laws sleep in the spare room where the server lives) and that would leave me with no DHCP which creates problems (when my in-laws want to get their laptop connected to the internet).

One answer is to get new in-laws which would be OK except that I'm still pretty keen on my wife.

Alternatively is there any way to set up a fallback DHCP server ie. the router would check if there's a functioning DHCP server on the network (ie. the fileserver) and if it gets no response it will serve DHCP addresses itself.

I've never done it, but it looks like this is what you want. You'd have to replace dnsmasq's dhcp with the isc-dhcp on your openwrt box, but it's one of the packages you can get through 'opkg'.

Good luck.

Great, that looks like what I need, I will give it a try.

Thanks.