I recently changed the IP address on an Ubuntu 12.04 server I have in my lab, which is running isc-dhcp-server. After doing so and modifying the dhcpd.conf file, my dhcp service would not start. I basically used the same configuration, except I modified everything to use /25 scopes rather than /24. When I try to start / restart the service, I see the following: MY@ubuntuserver:~$ sudo service isc-dhcp-server restart stop: Unknown instance: isc-dhcp-server start/running, process 20918 It looks like it starts, but it isn't actually running and Webmin states that the DHCP service is not running. So my question is, does isc-dhcp-server support subnetting (CIDR) style scopes, or must they be class A / B / C scopes (doesn't seem likely)? I've double checked the interface reference (this is a VM with only one defined eth0 interface) and everything else I can thing of.