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Difficulty: MediumIPv6 Address Types and EUI-64

A network administrator is verifying the IPv6 dynamic address configuration on a host interface. The host interface has a burned-in MAC address of `0012.7F34.5678`. Which two statements correctly describe the process and result of generating the interface identifier and IPv6 address using standard EUI-64?

  1. The hexadecimal string `FFFE` is inserted into the middle of the 48-bit MAC address to expand it to 64 bits.Answer
  2. The resulting 64-bit interface identifier for the host is `0212:7fff:fe34:5678`.Answer
  3. C
    The hexadecimal string `FFFF` is inserted into the middle of the MAC address to form the 64-bit interface identifier.
  4. D
    The first byte of the MAC address remains `00` in the interface identifier because it is a globally unique burned-in address.

Answer

The correct statements are that FFFE is inserted into the midpoint of the 48-bit MAC address and that the resulting 64-bit interface identifier is 0212:7fff:fe34:5678.
Generating an IPv6 EUI-64 interface identifier requires two key transformations on a 48-bit MAC address: inserting the hexadecimal value FFFE between the OUI and the vendor-assigned payload (the middle 16 bits) and inverting the 7th bit (Universal/Local bit) of the first byte. For MAC address 0012.7F34.5678, inserting FFFE produces 0012:7FFF:FE34:5678, and flipping the 7th bit converts the first byte from 00 to 02, producing 0212:7fff:fe34:5678.

Step-by-Step Solution

1
Split MAC address and insert FFFE
Splitting `00-12-7F` and `34-56-78` and placing `FF-FE` in the middle yields `00-12-7F-FF-FE-34-56-78`.
EUI-64 standard requires expanding a 48-bit MAC address to 64 bits by inserting FFFE into the middle.
2
Invert the 7th bit (Universal/Local bit)
The first byte `00` in binary is `0000 0000`. Inverting the 7th bit (bit index 1 from right in 0-indexed byte) yields `0000 0010`, which equals `02` in hex.
EUI-64 specifies that the 7th bit of the first byte must be inverted to indicate local scope within the IPv6 address framework.
3
Format as IPv6 Interface Identifier
Combining the modified first byte with the rest gives `0212:7fff:fe34:5678`.
IPv6 interface identifiers are formatted in four 16-bit hexadecimal quads separated by colons.

Key Concept

IPv6 EUI-64 Interface Identifier Derivation
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Topics

IPv6 Address Types and EUI-64

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