How is the interface ID of an IPv6 link-local address generated?

The interface ID of an IPv6 link-local address is generated primarily using the EUI-64 format, which constructs a unique identifier based on the device's MAC address. This process involves taking the 48-bit MAC address, inserting a fixed 16-bit value of FFFE in the middle, and flipping the 7th bit of the first byte to indicate that the address is globally unique.

By utilizing the EUI-64 method, devices can automatically generate their own link-local addresses without the need for manual configuration. This enhances the efficiency of setting up IPv6 environments, as devices can ensure their addresses are unique within the local network. While there are other methods to derive interface IDs, such as random generation or manual assignment, EUI-64 remains the standard for automatic address configuration in many scenarios, particularly on networks where devices have MAC addresses readily available.