Hello Muhammad
The EUI 64 method is one of several ways in which an interface can obtain an IPv6 address. Now EUI-64 process can be used to configure either a link-local IPv6 address OR a global unicast IPv6 address. The EUI-64 is the process used to determine those addresses. The specific process is further described in this lesson:
If applied to obtaining a link-local address, the address begins with fe80:0:0:0 as the first 64 bits, and the rest of the address is determined by the EUI-64 process.
If applied to obtaining a global unicast address, then it uses the desired network prefix, and adds the last 64 bits obtained via the EUI-64 process. This is further described in the SLAAC lesson below:
Now for the specific example, the reason that you see the EUI process in action is the fact that the solicited node multicast address was obtained using it’s IPv6 address as described in the lesson:
Every IPV6 device will compute a solicited node multicast address by taking the multicast group address (FF02::1:FF /104) and adding the last 6 hexadecimal characters from its IPv6 address. It will then join this multicast group address and “listens” to it.
But it’s IPv6 address was obtained using the EUI-64 process, and that is why you see the MAC address represented within the multicast address.
I hope this has been helpful!
Laz