Cisco Certified Network Associate (CCNA) Practice Exam

What is a method used to automatically generate the unique User Interface ID of an IPv6 address?

1. Extended Unique Identifier (EUI-64)

2. Dynamic Host Configuration (DHC)

3. Random Address Generation

4. IPv6 Static Assignment

The correct answer is: Extended Unique Identifier (EUI-64)

The Extended Unique Identifier (EUI-64) is a method specifically designed to automatically create a unique User Interface ID for an IPv6 address. This process involves taking a 48-bit MAC address and manipulating it into a 64-bit identifier. The steps include splitting the MAC address into two halves, inserting the hexadecimal value 'FFFE' in the middle, and inverting the seventh bit of the first byte of the original MAC address. Using the EUI-64 method ensures that each device on a network can generate its own interface ID in a way that is statistically unique. This auto-configuration capability is essential in large networks where manually assigning addresses would be impractical. Other methods mentioned, such as Dynamic Host Configuration (DHC), focus on assigning IP addresses dynamically from a central server, which does not generate unique interface IDs but rather leases IP addresses. Random Address Generation, while capable of creating unique addresses, does not follow a standardized process to ensure that IDs are based on hardware addresses, which can lead to potential conflicts. IPv6 Static Assignment involves manually configuring the addresses for devices, which isn't an automatic generation method. Thus, EUI-64 is the most effective choice for generating unique User Interface IDs automatically in the context of IPv6