MAC Validation

EtherLyzer can validate and normalize MAC-address input and produce character-level diagnostics for malformed values.

Validation and formatting are intentionally separate operations:

• validate interprets input and reports problems without typo correction.

• format --fix-typos may correct supported typo-like substitutions.

Validation masks

Validation diagnostics use a compact character-by-character mask.

Character itself	Position	Flag
Valid hexadecimal digit	Valid	v
Valid hexadecimal digit	Overflow	V
Relaxed substitution	Valid	r
Relaxed substitution	Overflow	R
Lenient substitution	Valid	l
Lenient substitution	Overflow	L
Invalid character	Anywhere	I
Missing character	Expected position	M

Lowercase substitution flags indicate a substitution candidate in a valid position.

Uppercase substitution flags indicate a substitution candidate in an overflow position (except M and I).

Examples

001a2b3c4d5     => vvvvvvvvvvvM
001a2b3c4d5e6   => vvvvvvvvvvvvV
0x1a2b3c4d5O    => vIvvvvvvvvvrM
001a2b3c4d5I    => vvvvvvvvvvvl

Missing digit

001a2b3c4d5     => vvvvvvvvvvvM

The input contains 11 hexadecimal digits. One hexadecimal digit is missing.

Overflow

001a2b3c4d5e6   => vvvvvvvvvvvvV

The first 12 hexadecimal digits occupy valid positions. The final digit exceeds the 12-digit EUI-48 length and is marked as overflow.

Invalid character and missing digit

0x1a2b3c4d5O    => vIvvvvvvvvvrM

The x is invalid and is marked with I.

The final O is recognized as a relaxed substitution candidate and marked with r. This leaves 11 usable hexadecimal positions, so the mask ends with M to indicate one missing digit.

Lenient substitution

001a2b3c4d5I    => vvvvvvvvvvvl

The first 11 characters are valid hexadecimal digits. The final character is recognized as a lenient substitution candidate and marked with l.