I've just been writing some guidance for our internal network that will help people to use manually-allocated MAC addresses rather than hardware ones.

In order to indicate that these are Locally Administered MAC addresses properly, I need to set the "second-least-significant but of the most significant byte of the address", and to make them normal Unicast addresses the last bit should be a zero; therefore the last two bits will be "10" and unless my calculator has died converting things :-) in the standard hex representation the second character must be one of 2,6,A or E ...

So to double-check, I grabbed the current OUI list from IEEE��http://standards.ieee.org/develop/regauth/oui/oui.txt and found 18 entries that match this pattern & therefore look like Local addresses.

$ egrep -i '^ +.[26AE]-' tmp/oui.txt��

�� 02-07-01 �� (hex) RACAL-DATACOM

�� 02-1C-7C �� (hex) PERQ SYSTEMS CORPORATION

�� 02-60-86 �� (hex) LOGIC REPLACEMENT TECH. LTD.

�� 02-60-8C �� (hex) 3COM CORPORATION

�� 02-70-01 �� (hex) RACAL-DATACOM

�� 02-70-B0 �� (hex) M/A-COM INC. COMPANIES

�� 02-70-B3 �� (hex) DATA RECALL LTD

�� 02-9D-8E �� (hex) CARDIAC RECORDERS INC.

�� 02-AA-3C �� (hex) OLIVETTI TELECOMM SPA (OLTECO)

�� 02-BB-01 �� (hex) OCTOTHORPE CORP.

�� 02-C0-8C �� (hex) 3COM CORPORATION

�� 02-CF-1C �� (hex) COMMUNICATION MACHINERY CORP.

�� 02-E6-D3 �� (hex) NIXDORF COMPUTER CORPORATION

�� AA-00-00 �� (hex) DIGITAL EQUIPMENT CORPORATION

�� AA-00-01 �� (hex) DIGITAL EQUIPMENT CORPORATION

�� AA-00-02 �� (hex) DIGITAL EQUIPMENT CORPORATION

�� AA-00-03 �� (hex) DIGITAL EQUIPMENT CORPORATION

�� AA-00-04 �� (hex) DIGITAL EQUIPMENT CORPORATION

(I also found a single 'multicast' value in there, but it doesn't seem to be a problem :-

$ egrep -i '^ +.[13579BDF]-' tmp/oui.txt��

�� 11-00-AA �� (hex) PRIVATE)

Some great old historical names on that list! Are these just relics of previous allocations, or are any of these in any meaningful way "live" in the real world?

-jim