Examkin

Question

Difficulty: MediumIPv6 Address Types and EUI-64

A network engineer executes the command `ipv6 address 2001:db8:abcd:1000::/64 eui-64` on a Cisco IOS router interface. The interface has a MAC address of `cc01.1a2b.3c4d`. Which IPv6 global unicast address will be assigned to this interface?

  1. 2001:db8:abcd:1000:ce01:1aff:fe2b:3c4dAnswer
  2. B
    2001:db8:abcd:1000:cc01:1aff:fe2b:3c4d
  3. C
    2001:db8:abcd:1000:ce01:1aff:ffff:3c4d
  4. D
    2001:db8:abcd:1000:cd01:1aff:fe2b:3c4d

Answer

The address 2001:db8:abcd:1000:ce01:1aff:fe2b:3c4d will be assigned to the interface.
The IPv6 address ending in ce01:1aff:fe2b:3c4d correctly applies both EUI-64 modifications: inserting FFFE into the middle of the 48-bit MAC address and inverting the 7th bit of the first byte (0xCC becomes 0xCE).

Step-by-Step Solution

1
Split the 48-bit MAC address into two 24-bit halves.
First half: cc:01:1a, Second half: 2b:3c:4d
EUI-64 generation requires splitting the MAC address at its midpoint to insert a 16-bit delimiter.
2
Invert the 7th bit (Universal/Local bit) of the first byte (0xCC).
0xCC (1100 1100 in binary) becomes 0xCE (1100 1110 in binary).
IEEE EUI-64 specifications require flipping the U/L bit (7th bit from the left) to indicate universal scope.
3
Insert hexadecimal FFFE between the two halves and format as IPv6 quads.
Interface ID: ce01:1aff:fe2b:3c4d
The 16-bit FFFE padding converts the 48-bit MAC address into a 64-bit interface identifier.
4
Combine the 64-bit prefix with the generated 64-bit interface ID.
2001:db8:abcd:1000:ce01:1aff:fe2b:3c4d
Appending the interface ID to the prefix produces the complete 128-bit IPv6 address.

Key Concept

EUI-64 Interface Identifier Derivation
Estimated Time:1m 15s
Rate this question

Topics

IPv6 Address Types and EUI-64

More questions from this topic