Jokes aside, a special "network calculator" mode when you type in e.g. a CIDR and it prints out an IP range or netmask, or when you type in a EUI-64 (MAC) and y

Jokes aside, a special "network calculator" mode when you type in e.g. a CIDR and it prints out an IP range or netmask, or when you type in a EUI-64 (MAC) and you get a link-local address would be awesome. It's all almost a no-brainer but only "almost" - I always tend to forget the exact rules (e.g. where exactly that FF:FE goes in).