How is the interface ID generated when using SLAAC?

The interface ID in Stateless Address Autoconfiguration (SLAAC) is generated primarily using the EUI-64 format or may be assigned randomly. When EUI-64 is used, the host's MAC address is incorporated into the interface ID by expanding it into a 64-bit format. This process involves inverting the seventh bit of the MAC address and inserting the hexadecimal value 'FFFE' in the middle of the address, facilitating unique interface IDs.

Alternatively, when privacy considerations are taken into account, operating systems may opt to generate a random interface ID instead of creating it from the MAC address. This enhances user privacy by making it more difficult for external observers to track devices based solely on their IP addresses. The combination of these two methods provides flexibility and addresses security considerations in IP address assignment within IPv6 networks.