I want to force a netmask on my Ubuntu machine. For example, I want 11.0.0.1 to get a netmask of 255.255.255.0 I tried editing /etc/network/interfaces and I forced the desired netmask, but as soon as I restarted the interfaces it changed it back to the default value. When I used ifconfig the netmask that I gave survived the interface restart but it was reset as soon as I rebooted the machine. Is there a way to force an "illegal" netmask on an interface?