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Difficulty: MediumIPv6 Address Types and EUI-64

An administrator enables IPv6 autoconfiguration on a network host interface with a burned-in hardware MAC address of 70-69-5A-12-34-B5. Which two statements regarding the generated EUI-64 interface identifier and link-local address are correct?

  1. The generated interface identifier is 7269:5aff:fe12:34b5.Answer
  2. The automatically assigned link-local address uses the prefix fe80::/10.Answer
  3. C
    The 16-bit hexadecimal string ffff is inserted between the OUI and the device identifier.
  4. D
    The 7th bit of the first byte remains unchanged as 0 to indicate a universally administered address.

Answer

The correct statements are that the generated interface identifier is 7269:5aff:fe12:34b5 and the link-local address uses the prefix fe80::/10.
Generating an IPv6 EUI-64 interface identifier from a 48-bit MAC address requires splitting the MAC address into two 24-bit halves, inserting fffe into the middle, and inverting the 7th bit (Universal/Local bit) of the first byte. For the MAC 70-69-5A-12-34-B5, the byte 70 (0111 0000) becomes 72 (0111 0010), producing the interface ID 7269:5aff:fe12:34b5. Furthermore, all IPv6 link-local autoconfigured addresses use the standardized prefix fe80::/10.

Step-by-Step Solution

1
Split the 48-bit MAC address into two 24-bit halves
Left half: 70-69-5A, Right half: 12-34-B5
EUI-64 creation requires inserting a fixed 16-bit value between the Organizationally Unique Identifier (OUI) and the NIC-specific identifier.
2
Insert the hexadecimal string fffe between the two halves
7069:5AFF:FE12:34B5
The IEEE EUI-64 standard specifies the insertion of FFFE into the midpoint of a 48-bit MAC address.
3
Invert the 7th bit (Universal/Local bit) of the first byte
Hex 70 (binary 0111 0000) becomes Hex 72 (binary 0111 0010), yielding the interface ID 7269:5aff:fe12:34b5
In EUI-64 formatting, the 7th bit of the first octet is inverted to indicate local scope/modification.
4
Combine the interface identifier with the IPv6 link-local prefix
fe80::7269:5aff:fe12:34b5 (prefix range fe80::/10)
Link-local addresses in IPv6 use the reserved prefix range fe80::/10.

Key Concept

IPv6 EUI-64 Interface Identifier Derivation and Link-Local Addressing
Estimated Time:1m 30s
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Topics

IPv6 Address Types and EUI-64

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