ISC DHCP has a PREINIT script to solve this situation but I don't understand how you can get an interface down on a server (PREINIT scripts are for clients). IMHO you should launch Kea only when the interface is UP, RUNNING and has an IPv4 address (it seems it doesn't matter this address is 0.0.0.0). Regards Francis Dupont <fdupont at isc.org>