EUI-64 Interface ID Calculation for Router R2 (Segment 7)

200-301 By islever Editorial Last updated

Configure and verify IPv6 addressing and prefix

Short answer

A Applying EUI-64 to R2's MAC yields 2001:db8:9bb6:6bb9:C801:B6FF:FEB4:1.

Question

Refer to the exhibit. The IPv6 address for the LAN segment on router R2 must be configured using the EUI-64 format. When configured which ipv6 address is produced by the router? - Exhibit: EUI-64 Interface ID Calculation for Router R2 (Segment 7)
  1. 2001:db8:9bb6:6bb9:C801:B6FF:FEB4:1 Correct Answer
  2. 2001:db8:9bb6:6bb9:C001:6BFE:FF01:1
  3. 2001:db8:9bb6:6bb9:C081:B6FF:FF4B:1
  4. 2001:db8:9bb6:6bb9:4736:931F:FE37:1

Key Takeaways

Consistent with the bank's EUI-64 questions: the answer shows C8 (inverted bit) and the FFFE position (B6FF). A is the only option with both.

EUI-64: split the MAC, insert FFFE, and invert the seventh bit. R2's first byte becomes C8, giving C801; the FFFE insertion gives B6FF; the host half completes to FEB4, matching option A.

Common mistake: Picking B/C (C001/C081 miss the inversion) or D (no FFFE/inversion present).

Expert Analysis

Why the Answer Is Correct

A is correct. EUI-64 on R2's MAC: the first byte CA (1100 1010) flips its seventh bit to 1100 1000 = C8, so the interface ID starts with C801, and the FFFE insertion produces B6FF, yielding 2001:db8:9bb6:6bb9:C801:B6FF:FEB4:1.

Why the Other Options Are Wrong

B (C001) and C (C081) miss the seventh-bit inversion, so their first hextet is wrong. D does not follow the EUI-64 transformation.

Community Comment Notes

The vote is A (100). Commenters repeatedly note 'invert the 7th bit: CA becomes C8,' confirming C801:B6FF as the correct form.

Official Reference

https://learningnetwork.cisco.com/s/ccna-exam-topics

This link opens the official vendor documentation in a new tab.

Community Votes

A
100%

100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 8 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 8

  1. exiledwl 👍 2 Answered A
    With the number of times we've seen this exact question in the bank, we better get it at least once on exam
  2. Blumen 👍 1 Answered A
    CA - 1100 1010 Invert 7th bit => 1100 1000 => C8 Hence, the correct answer is A...
  3. kitannnnn 👍 1 Answered A
    ca = 11001010 inverted 7th bit = 11001000 = c8 ans = c801:b6ff:feb4:1
  4. cybercerberes 👍 1 Answered A
    Add FF:FE beetwen B6 B4 in this case and you find IPv6 EUI-64
  5. bezkin 👍 1 Answered A
    remember 7th bit For Figuring Fast Eui64 (7th bit FFFE)
Show 3 more comments
  1. ekansh_m 👍 1 Answered A
    Correct answer is A. 7th bit of “a” is inverted to an 8
  2. Ras_Al_Ghul 👍 1 Answered A
    convert 7th bit cA becomes c8 .
  3. exiledwl 👍 1 Answered A
    A is right

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