Examkin

Question

Difficulty: MediumIPv6 Addressing and Prefixes

A network administrator configures a Cisco router interface using the command `ipv6 address 2001:db8:4444:5555::/64 eui-64`. If the MAC address of the interface is 0800.2765.43210800.2765.4321, which full IPv6 global unicast address is generated for this interface?

  1. 2001:db8:4444:5555:a00:27ff:fe65:4321Answer
  2. B
    2001:db8:4444:5555:800:27ff:fe65:4321
  3. C
    2001:db8:4444:5555:a00:27ff:ffff:4321
  4. D
    2001:db8:4444:5555:a00:27ff:fe65:4320

Answer

2001:db8:4444:5555:a00:27ff:fe65:4321
The correct IPv6 address is constructed by taking the MAC address 0800.2765.4321, inserting FFFE between the third and fourth bytes to form 0800:27FF:FE65:4321, and flipping the 7th bit of the first byte (changing 08 to 0A). Compressing the leading zero of 0A00 produces a00:27ff:fe65:4321, which appends to the prefix 2001:db8:4444:5555::/64.

Step-by-Step Solution

1
Split the 48-bit MAC address into two 24-bit halves and insert FFFE in the middle.
MAC address 0800.2765.4321 becomes 0800:27FF:FE65:4321.
EUI-64 generation requires expanding a 48-bit MAC address into a 64-bit interface ID by inserting FFFE into the center.
2
Invert the 7th bit (universal/local bit) of the first octet.
First octet 08 in hex is 0000 1000 in binary. Flipping the 7th bit yields 0000 1010 in binary, which is 0A in hex. The identifier becomes 0A00:27FF:FE65:4321.
IEEE EUI-64 rules mandate flipping the 7th bit of the MAC address to indicate universal scope.
3
Combine the /64 IPv6 prefix with the EUI-64 interface ID and apply RFC 4291/5952 zero compression rules.
Prefix 2001:db8:4444:5555::/64 + Interface ID 0a00:27ff:fe65:4321 = 2001:db8:4444:5555:a00:27ff:fe65:4321.
Leading zeros in any 16-bit hexadecimal field are omitted (0a00 becomes a00).

Key Concept

EUI-64 Interface Identifier Generation
Estimated Time:1m 30s
Rate this question

Topics

IPv6 Addressing and Prefixes

More questions from this topic