IPv6 interface ID on serial connections

in CCNA & CCENT
Hi guys,
I've just read a chapter on IPv6 and was wondering how a serial interface gets an interface ID. From what I understood, this is part of autoconfiguration which uses EUI-64 where a MAC address gets padded with FFFE. I thought that only Ethernet has MAC addresses so how does this address get created?
I've just read a chapter on IPv6 and was wondering how a serial interface gets an interface ID. From what I understood, this is part of autoconfiguration which uses EUI-64 where a MAC address gets padded with FFFE. I thought that only Ethernet has MAC addresses so how does this address get created?