IPv6 interface identifier???? EUI-64

aueddonline

IPv6 interface identifier

ok so here's the example in the book

MAC

00-11-2F-1D-1B-48

make the EUI-64

00-11-2F-FF-FE-1D-1B-48

and with the 7th bit of the first byte binary 1 making

02-11-2F-FF-FE-1D-1B-48

Here's my question, does the fact that there is a binary 1 in the 7th (U/L) bit tell us that the address is globally unique? or is it the other way round?

dtlokee

I was told the U/L bit should be set to "1" if you ever change the MAC address of a NIC to ensure it won't match the address of another NIC. That would seem to indicate the U/L bit set to "0" means it is globally unique (maybe just referring to the last 40 bits and not all 48?)

aueddonline

cool, that's what I thought, there's no reason to ever want to change the MAC address in use really I guess, not that I can think of

dtlokee

We would change them on devices like printers when we replaced the NIC in the printer because the clients were connecting via DLC and the MAC address, and I guess you can make a case for doing it when poer security os in use and you are replacing host machines.