Sorry fot the top-post, but my Treo makes it almost impossible to do otherwise. The protocols using these reserved, local addresses all use them to embed the network layer address. AA addresses are used by DECnet and kin while 02 is for XNS, I seem to recall. As long as the only addresses used in these spaces are thse asigned by those protocols and they use peoperly assigned network layer addresses, ther will never be a conflict. That is the point in0the registration...marking them as reserved for the protocols in question and not to be used for anything else. Sent from my Treo: R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) E. O. Lawrence Berkeley National Laboratory (LBNL) oberman@es.net +1 510-486-8634 -----Original Message----- From: Saku Ytti <saku+nanog@ytti.fi> Date: Wednesday, Mar 4, 2009 12:49 am Subject: Re: MAC address confusion To: nanog@nanog.org On (2009-03-03 13:50 -0800), Kevin Oberman wrote:

This is only a problem if you have multiple systems running DECnet (or some other protocol using this) with the same layer 3 address. That should never happen, so there should be no duplication.

Why would they need to have same L3 address? The way I see it, only thing that matters is, if or not, the addresses might speak ethernetII. If your ethernetII switch sees your local 02 address and one of the addresses below and they collide, the switch will keep relearning the address behind two ports. Unless of course it is guaranteed, that none of these addresses will ever appear as BIA in ethernetII capable NIC. 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 -- ++ytti