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Difficulty: MediumIPv6 Addressing Concepts and Header Structure

A network administrator is verifying the automatic IPv6 interface configuration of a host. The host network adapter has a MAC address of 00:1A:2B:3C:4D:5E. Which IPv6 link-local address is generated for this interface using the Modified EUI-64 format?

  1. fe80::21a:2bff:fe3c:4d5eAnswer
  2. B
    fe80::01a:2bff:fe3c:4d5e
  3. C
    fe80::21a:2b00:fe3c:4d5e
  4. D
    fe80::001a::2bff:fe3c:4d5e

Answer

fe80::21a:2bff:fe3c:4d5e
To form a Modified EUI-64 interface identifier from a 48-bit MAC address, the 16-bit sequence FFFE is inserted between the OUI and NIC specific bytes, and the 7th bit of the first byte is inverted (changing 00 to 02). When prefixed with fe80::/64 and formatted with standard zero suppression, the resulting address is fe80::21a:2bff:fe3c:4d5e.

Step-by-Step Solution

1
Divide the 48-bit MAC address into two 24-bit halves.
Left half: 00:1A:2B, Right half: 3C:4D:5E.
Modified EUI-64 creates a 64-bit interface identifier by inserting a fixed 16-bit value between the OUI and the device's extension identifier.
2
Insert the 16-bit hexadecimal string FFFE between the two halves.
00:1A:2B:FF:FE:3C:4D:5E.
The standard EUI-64 expansion rule requires adding FFFE into the center of a 48-bit MAC address.
3
Invert the 7th bit (universal/local bit) of the first byte.
The first byte 0x00 (00000000 in binary) becomes 0x02 (00000010 in binary).
IPv6 Modified EUI-64 rules require flipping the 7th bit of the first byte to indicate universal scope.
4
Combine the result with the link-local prefix (fe80::/64) and apply standard zero compression.
fe80::21a:2bff:fe3c:4d5e.
Leading zeros within a 16-bit hex block (021a to 21a) are omitted according to RFC 5952 formatting standard.

Key Concept

Modified EUI-64 Link-Local Address Generation
Estimated Time:1m 30s
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Topics

IPv6 Addressing Concepts and Header Structure

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