what is an interface id
The second part of an IPv6 unicast or anycast address is typically a 64-bit interface identifier used to identify a hostâs network interface. A 64-bit interface ID is created by inserting the hex number FFFE in the middle of the MAC address of the network card. Also, the 7th Bit in the first byte is flipped to a binary 1 (if the 7th bit is set to 0 it means that the MAC address is a burned-in MAC address.). When this is done, the interface ID is commonly called the modified extended unique identifier 64 (EUI-64).