200-301 Question 115
Select 3A network engineer is configuring an IPv6 link-local address on an interface and decides to use the Modified EUI-64 format for automatic address generation. The MAC address of the interface is 00:1A:2B:3C:4D:5E. Which of the following steps are part of the process for generating the IPv6 address using the Modified EUI-64 format?
- A
Insert the hexadecimal value FFFE in the middle of the MAC address.
- B
Change the seventh bit of the first byte of the MAC address to 1.
- C
Prefix the MAC address with the network portion FE80::/64.
- D
Reverse the order of the bytes in the MAC address.
- E
Convert the MAC address from hexadecimal to decimal.
Show answer and explanation
Correct answers: A, B, C
Explanation
The Modified EUI-64 format is used to generate an interface identifier for IPv6 addresses by expanding a 48-bit MAC address into a 64-bit value. This involves inserting FFFE in the middle of the MAC address, flipping the seventh bit of the first byte, and prefixing the result with the appropriate network portion (FE80::/64 for link-local addresses).
- A. Correct.
Correct. In the Modified EUI-64 process, FFFE is inserted in the middle of the MAC address to expand it to 64 bits.
- B. Correct.
Correct. The seventh bit of the first byte (Universal/Local bit) is flipped to indicate that the address is globally unique.
- C. Correct.
Correct. The link-local address is always prefixed with FE80::/64 in IPv6.
- D. Incorrect.
Incorrect. The order of the MAC address bytes is not reversed during the Modified EUI-64 process.
- E. Incorrect.
Incorrect. The MAC address remains in hexadecimal format; no conversion to decimal is performed.