In my studies to being prepared to obtain the CCNP, I’ve been surprised by the quantity of materials on internet who are mistaken on a little detail about the generation of the IPv6 address when they show how to build and EUI-64 address.
The last 64 bits of and IPv6 address could be formed as a modified EUI-64 in the link-local and global address.
So as the normal transformation of a MAC (48 bits) into a EUI-64 you add right into the middle, between the company and vendor id “FF:FE”. The oversight come just after, where they forget to explain than also the Local/Global bit (7º) should be marked as a 1. With this, it would be easier to know if it’s or not an auto-generated address.
You can find more information about it in http://tools.ietf.org/html/rfc5342 http://tools.ietf.org/html/rfc4291 and http://en.wikipedia.org/wiki/IPv6_address
After an ifconfig you should be able to see something like this on your computer
eth0 Link encap:Ethernet HWaddr 00:19:bb:d1:f0:2d
inet6 addr: fe80::219:bbff:fed1:f02d/64 Scope:Link
So now we are going to transform our MAC address into the last 64 bits as you could see above.
1. Adding fffe between the company and vendor id.
00:19:bb:d1:f0:2d -> 00:19:bb:ff:fe:d1:f0:2d
2. Changing the Local/Global bit to one
00 in hexadecimal is 0000 0000 in binary and we need to change the seventh one.
0000 0010 -> 02
3. Converting the address into the IPv6 format
02:19:bb:ff:fe:d1:f0:2d -> 219:bbff:fed1:f02d
I hope it help you 