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Difficulty: MediumIPv6 Address Types and EUI-64

A Cisco router interface with MAC address 0011.4567.89ab is configured to dynamically derive its IPv6 interface identifier using EUI-64. What is the resulting 64-bit interface identifier in standard colon-separated hexadecimal IPv6 format?

Answer: 0211:45ff:fe67:89ab / 211:45ff:fe67:89ab

Answer

0211:45ff:fe67:89ab
To derive a 64-bit IPv6 interface identifier from the 48-bit MAC address 0011.4567.89ab using EUI-64: 1) Insert FFFE into the middle of the MAC address, yielding 0011:45FF:FE67:89AB. 2) Invert the 7th bit (Universal/Local bit) of the first octet. The first octet 0x00 (0000 0000 in binary) becomes 0x02 (0000 0010 in binary). Combining these steps yields the final interface identifier 0211:45ff:fe67:89ab (or 211:45ff:fe67:89ab without leading zero).

Step-by-Step Solution

1
Split the 48-bit MAC address into two 24-bit halves.
First half: 00:11:45, Second half: 67:89:ab
EUI-64 calculation begins by separating the Organizationally Unique Identifier (OUI) from the vendor-assigned NIC portion.
2
Insert the 16-bit hexadecimal string FFFE between the two halves.
0011:45FF:FE67:89AB
IEEE EUI-64 conversion requires expanding the 48-bit MAC address into a 64-bit value by inserting FFFE at the midpoint.
3
Invert the 7th bit (Universal/Local bit) of the first byte.
First byte 0x00 (binary 00000000) becomes 0x02 (binary 00000010), producing 0211:45ff:fe67:89ab.
Inverting the U/L bit sets it to 1, indicating that the IEEE MAC-derived interface ID is globally unique.

Key Concept

IPv6 EUI-64 Interface Identifier Derivation
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Topics

IPv6 Address Types and EUI-64

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