<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Andale Mono; font-size: 10pt; color: #000000'><font face="'Andale Mono'" size="2">It SEEMS like the windows machine is using the MAC although I am not sure of DUID vs IAID and where each can be seen.</font><div style="color: rgb(0, 0, 0); font-family: 'Andale Mono'; font-size: 10pt; "><br></div><div style="color: rgb(0, 0, 0); font-family: 'Andale Mono'; font-size: 10pt; ">I just disabled / enabled adapter on test windows7 laptop here ... I have some numbers available (sans packet capture) from logs and from the leases file (dhcpd ):</div><div style="color: rgb(0, 0, 0); font-family: 'Andale Mono'; font-size: 10pt; "><br></div><div><font face="'Andale Mono'" size="2"><b>00:15:c5:14:ce:b0</b> (the actual mac of the windows computer)</font></div><div><font face="'Andale Mono'" size="2">dhcpd: Client <u>00:01:00:01:13:e0:fd:f1:<b>00:15:c5:14:ce:b0</b></u> releases address 2620:0:2e50:e8:1::f541 (line from the log file - I assume that is DUID - seems to contain full mac)</font></div><div><font face="'Andale Mono'" size="2">ia-na "\305\025\000\020\000\001\000\001\023\340\375\361\000\025\305\024\316\260" (Opener to the lease entry in leases file - i have no idea what that string of stuff is)</font></div><div><br><div style="color: rgb(0, 0, 0); font-family: 'Andale Mono'; font-size: 10pt; "><br></div><hr id="zwchr" style="color: rgb(0, 0, 0); font-family: 'Andale Mono'; font-size: 10pt; "><blockquote style="border-left-width: 2px; border-left-style: solid; border-left-color: rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; color: rgb(0, 0, 0); font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica, Arial, sans-serif; font-size: 12pt; "><b>From: </b>"Michael Dean Pugh" <mdpugh@hotmail.com><br><b>To: </b>dhcp-users@isc.org<br><b>Sent: </b>Wednesday, January 25, 2012 3:00:05 PM<br><b>Subject: </b>Re: DHCPv6 and MAC Address inclusion<br><br>I'm jumping in at the end here and not responding to any particular post. I <br>have followed this thread with great interest. This seems like a good time to <br>make an observation and ask a question.<br><br>There is much talk about deriving the MAC address from IPv6 identifiers. <br>While it's true that in most cases (every case I've personally observed--<br>Windows and FreeBSD) the MAC is part of the DUID, this is only useful if the <br>host has one interface as the DUID is unique to the host not the interface (I <br>think we're all in agreement here). Also, once the host has assigned itself <br>the DUID, the interface can be replaced, but the DUID will remain the same, so <br>the MAC address derived from the DUID at this point would be invalid. Again, <br>this is with Windows and FreeBSD.<br><br>Now, the observation. Microsoft encodes the first 24 bits of the MAC address <br>(the manufacturer portion) in the IAID by directly copying them into the last <br>24 bits of the IAID. In other words, if the MAC is 01:23:45:ab:cd:ef, the <br>IAID is xy012345(Hex) for some x and y. This has limited usefulness since it <br>is entirely possible to have more than one interface from the same <br>manufacturer installed in one host (it seems like it would have made more <br>sense to have used the last 24 bits of the MAC).<br><br>This brings me to the question. Does anyone know how the first 8 bits of the <br>IAID are derived by Microsoft? I'm pretty sure I found this somewhere on the <br>Internet, but have been unable to find it again. I'm also wondering if <br>Microsoft's IAID algorithm is based on any standards or if the IAID is merely <br>a 32-bit number. It does seem that the IAID holds enough information to <br>uniquely identify each interface on a single managed network.<br><br><br><br>_______________________________________________<br>dhcp-users mailing list<br>dhcp-users@lists.isc.org<br>https://lists.isc.org/mailman/listinfo/dhcp-users<br><br></blockquote><br></div></div></body></html>