It'd be nice if network configuration could autofill-in the netmask based upon the ip address you've already entered: Class IP Range Netmask A 1-126.0.0.0 255.0.0.0 B 128-191.0.0.0 255.255.0.0 C 192-223.0.0.0 255.255.255.0 D 224-254.0.0.0 [multicast only] The following is redundant but useful knowledge. IP Address Ranges reserved for non-Internet use Class IP Range Netmask A 10.0.0.0 - 10.255.255.255 255.0.0.0 B 172.16.0.0 - 172.31.255.255 255.255.0.0 C 192.168.0.0 - 192.168.255.255 255.255.255.0