During the IPv6 autoconfiguration, what does the device append to the 64-bit prefix that it
receives from the router to create its IPv6 address? Select the best response.

A.
a pseudorandom generated number

B.
its locally configured IPv4 address

C.
the DHCP-supplied device ID

D.
its MAC address

Explanation:
The automatic configuration is a great feature of IPv6. Imagine you have to manually
configure an IPv6 address with 128-bit long, what apain! With this feature, it is no longer
necessary to configure each host manually. But notice that host only autonomously
configures its own Link-local address (the IP address used on a LAN). The Link-local
address can be created automatically using a link-local prefix of FE80::/10 and a 64-bit
interface identifier (based on 48-bit MAC address).
For example, if your MAC address is 00:12:34:56:78:9a, your 64-bit interface identifier is
0012:34FF:FE56:789a (16-bit FFFE is inserted in themiddle). And notice that the notation
has been changed because IPv6 addresses require 16-bit pieces to be separated by “:”.
Then, according to the RFC 3513 we need to invert the Universal/Localbit (“U/L” bit) in the
6th position of the first octet (start counting from 0). The “u” bit is set to 1 to indicate
Universal, and it is set to zero (0) to indicate local scope. In this case we set this bit to 1
because the MAC address is universally unique. Thusthe result is: 0212:34FF:FE56:789a.
Finally, add the link-local prefix FE80 to create the full IPv6 address:
FE80:0:0:0:0212:34FF:FE56:789a (or FE80::212:34FF:FE56:789a, in short form).
Note: The reason for inverting the “U/L” bit is to allow ignoring it for short values in the
manual configuration case. For example, you can manually assign the short address fc80::1
instead of the long fc80:0:0:0:0200::1.