Work out ipv6 eui 64 instantly with clear inputs, formula shown and shareable results.
Modified EUI-64 turns a 48-bit MAC into a 64-bit interface identifier by inserting FFFE between the OUI and the NIC halves and inverting bit 1 of the first byte, the universal/local flag. Combined with a /64 prefix it produces the address that stateless autoconfiguration would assign, and with fe80:: it gives the link-local address.
Modified EUI-64
IID = (byte1 XOR 0x02) : byte2 : byte3 : FF : FE : byte4 : byte5 : byte6
In EUI-64 the bit means universal when set, the opposite of the MAC convention, so inverting keeps globally unique MACs mapping to universally scoped identifiers.
Many now prefer RFC 7217 stable opaque identifiers or RFC 8981 temporary addresses for privacy, but EUI-64 remains the default on plenty of routers and embedded stacks.