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Difficulty: MediumIPv6 Address Types and EUI-64

A network host generates its IPv6 link-local address using stateless address autoconfiguration (SLAAC) and the standard IEEE EUI-64 process. If the Ethernet interface has a burned-in MAC address of `0800.27a4.12b3`, what is the resulting IPv6 link-local address assigned to the interface?

  1. fe80::a00:27ff:fea4:12b3Answer
  2. B
    fe80::800:27ff:fea4:12b3
  3. C
    fe80::a00:27ff:ffa4:12b3
  4. D
    fe80::200:27ff:fea4:12b3

Answer

The resulting link-local address is fe80::a00:27ff:fea4:12b3.
The correct option correctly converts the MAC address `0800.27a4.12b3` into an EUI-64 interface identifier by inserting `FFFE` into the middle (`0800:27FF:FEa4:12b3`) and toggling the 7th bit of the first byte (`0x08` to `0x0A`). Prepending the `fe80::` link-local prefix results in `fe80::a00:27ff:fea4:12b3`.

Step-by-Step Solution

1
Split the 48-bit MAC address into two 24-bit halves and insert FFFE into the midpoint.
The MAC address `08-00-27-a4-12-b3` becomes `0800:27FF:FEA4:12B3`.
EUI-64 requires expanding a 48-bit MAC address into a 64-bit interface identifier by placing FFFE between the OUI and the vendor-assigned payload.
2
Invert the 7th bit (Universal/Local bit) of the first byte.
First byte `0x08` (`0000 1000` in binary) has its 7th bit inverted to become `0000 1010` (`0x0A`).
IEEE EUI-64 rules dictate that the 7th bit of the first byte must be inverted (0 for global uniqueness becomes 1 for local scope in IPv6).
3
Prepend the standard link-local network prefix fe80::/10.
The complete IPv6 link-local address is `fe80::a00:27ff:fea4:12b3` (leading zeroes in hex blocks are omitted per standard IPv6 notation).
Link-local addresses generated via SLAAC automatically use the prefix fe80::/10 followed by 54 zero bits and the 64-bit EUI-64 interface identifier.

Key Concept

EUI-64 Interface Identifier Generation and IPv6 Link-Local Addressing
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Topics

IPv6 Address Types and EUI-64

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