Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!pacbell.com!decwrl!nsc!voder!blia!ted From: ted@blia.BLI.COM (Ted Marshall) Newsgroups: comp.sys.dec Subject: Re: DECNET MAC address use query Message-ID: <12925@blia.BLI.COM> Date: 10 Nov 90 03:28:07 GMT References: <1990Nov8.125106.18326@gdr.bath.ac.uk> Organization: Britton Lee, Los Gatos, CA Lines: 23 In article <1990Nov8.125106.18326@gdr.bath.ac.uk>, exspes@gdr.bath.ac.uk (P E Smee) writes: > We are told that DEC, rather than assigning a single MAC address to a > given machine, assigns a group of MAC address to each box, so that the > DECNET protocol can use some of the 'address' bits to send small > control messages around. (I find this distasteful, but apparently it's > 'legal' as long as they stick to their assigned address range.) Whomever told you that is dead wrong! A machine running DECnet has its Ethernet address set based on the DECnet address (see below). Each machine has a single address only. Multicast addresses in the range AB-00... are also used but not as station addresses. The station address is set as follows: The first 4 bytes are AA-00-04-00. The last two bytes are computed as (area * 1024 + node), byte swapped. Thus, DECnet address 8.56 would compute as (8 * 1024 + 56) = 8248 = 0x2038. Thus, the corresponding Ethernet address would be AA-00-04-00-38-20. Hope this helps. -- Ted Marshall ...!ucbvax!mtxinu!blia!ted ted@blia.bli.com ShareBase Corp., 14600 Winchester Blvd, Los Gatos, Ca 95030 (408)378-7000 The opinions expressed above are those of the poster and not his employer.