MAC address formatter

Reformats MAC addresses into any of the four common styles: colon-separated, hyphen-separated, Cisco’s four-digit dotted groups, or no separator at all.

The four styles exist because different vendors chose differently and none gave way: Linux and most standards use colons, Windows and IEEE documents use hyphens, Cisco uses three groups of four separated by dots, and raw hex turns up in configuration files and logs. They are the same forty-eight bits either way. Only the digits are read here, so any input style is accepted and only the output style is your choice. Anything that is not exactly twelve hexadecimal digits is rejected rather than padded, because a MAC address with the wrong number of digits is a typo and guessing which digit is missing would be worse than saying so.