CISSP All Domains Practice test 7

We are planning our move from IPv4 to IPv6 internally in our organization. An executive asks if we can still use our older devices with MAC/EUI-48 addresses. You answer, "Yes, IPv6 just adds FFFE to the MAC/EUI-48 address, effectively making it a MAC/EUI-64 address." Where is the FFFE added to the MAC/EUI-48 address?