IPv6 Interface ID
The host portion of the address is last 64 bits. It can be assigned manually,
using DHCP v6, or using stateless autoconfiguration.
An end-system uses stateless autoconfiguration by waiting for a router to
advertise the local prefix. If the end system has a 64-bit MAC, it concatenates
the prefix and its MAC to form an IPv6 address. If the end system has
a 48-bit MAC, it flips the global/local bit and inserts 0xFFEE into the
middle of the MAC. The resulting 64-bit number is called the EUI64. The
prefix and EUI64 are concatenated to form the address. Figure 8-2 shows
how a host uses its MAC address to create its IPv6 address.