/^[\da-f][\da-f]:
  [\da-f][\da-f]:
  [\da-f][\da-f]:
  [\da-f][\da-f]:
  [\da-f][\da-f]:
  [\da-f][\da-f]$/ix

##</code><code>##

/^
  (?:
     [\da-f]{2}:
   ){5}
  [\da-f]{2}
$/ix;