Building the EUI-64 Interface Identifier for Router R2

Answer Correct answer: D — Applying EUI-64 (split MAC, insert FFFE, invert 7th bit) to R2's MAC yields 2001:db8:9bb6:6bb9:C801:B6FF:FEB8:1.

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? - image

  1. 2001:db8:9bb6:6bb9:C081:B6FF:FF4B:1
  2. 2001:db8:9bb6:6bb9:C001:6BFE:FF01:1
  3. 2001:db8:9bb6:6bb9:4679:824F:FE88:1
  4. 2001:db8:9bb6:6bb9:C801:B6FF:FEB8:1 Correct Answer

Community Votes

D
100%

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

Community Insight

As with the other EUI-64 questions, the answer shows the inverted seventh bit (C8, not C0/C2) and the FFFE insertion; D is the only option consistent with that transformation.

EUI-64 builds the interface ID from the MAC: split at the OUI/host boundary, insert FFFE, and flip the seventh bit (U/L) of the first byte. For R2 the inverted first byte becomes C8, placing C801 in the third hextet, matching option D.

Picking an option whose first hextet lacks the C8 (inverted-bit) result. The 7th-bit flip is the step most often missed.

Community Discussion (9 comments)

exiledwl 👍 2 Selected: D
D for sure
1625b6d 👍 1 Selected: D
Answer is D
bymrdas 👍 2 Selected: D
D is Correct
KuyaErik101 👍 1
c801:bfff:fea4:1 - the correct answer nearest is D
d5c03de 👍 1
It's D fam
askar430 👍 1 Selected: D
its D , C8
ladarius01 👍 1
1. Split MAC in half and insert FF FE. 2. Invert 7th bit: a = 1010 - > 1000 = 8
JulesAZ 👍 3 Selected: D
Can be the only answer using the rules for these questions. The fact that the question / solution, is wrong just does my head in!! DDDDD
picho707 👍 2 Selected: D
Correct answer is D. CA = 1100 1010 so flipping the 7 bit => 1100 1000 = C8

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Expert Analysis

Why the Answer Is Correct

D 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 begins with C801, and the FFFE insertion produces the remainder shown in D (2001:db8:9bb6:6bb9:C801:B6FF:FEB8:1).

Why the Other Options Are Wrong

A (C081) and B (C001) miss the seventh-bit inversion, so their first hextet is wrong. C does not follow the EUI-64 transformation of the exhibited MAC at all.

Community Comment Notes

The vote is D (100). Commenters derive CA -> C8 by flipping the seventh bit, confirming C801 as the correct start and noting D is the only option that follows the EUI-64 rules.

Official Reference

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