# File lib/faker/internet.rb, line 89
      def mac_address(prefix='')
        prefix_digits = prefix.split(':').map{ |d| d.to_i(16) }
        address_digits = (6 - prefix_digits.size).times.map{ rand(256) }
        (prefix_digits + address_digits).map{ |d| '%02x' % d }.join(':')
      end