Comment 7 for bug 26822

I haven't read the RFC recently, but it would seem to me that the DHCP server ought to hand out the IP address it gave to PXE again when the Ubuntu client asks, or at least reuse the same address when PXE asks the 2nd time.

Failing that, configuring the Edubuntu server to hand out 30s (say) leases by default, and longer ones to actual Ubuntu clients, would be an approximation to what mdz suggests.

Note that to be guaranteed not to fail this approach does need an address pool ((default timeout) / (time from hard reboot to PXE DHCP request)) times the number of machines you have, which is rather unfortunate.