IPv6 EUI-64 Address Generation from MAC Address

H12-811 By islever Editorial Last updated

IP Addressing and Configuration

Short answer

A The EUI-64 address is 02E0-FCFF-FEEF-0FEC, derived by inserting FFFE in the middle of the MAC and inverting the 7th bit of the first byte.

Question

If the MAC address of an interface is 00E0-FCEF-0FEC, the corresponding EUI-64 address is ( ).
  1. 02E0-FCFF-FEEF-0FEC Correct Answer
  2. 02E0-FCEF-FFFE-0FEC
  3. 00E0-FCFF-FEEF-0FEC
  4. 00E0-FCEF-FFFE-0FEC

Key Takeaways

The core test is the two-step EUI-64 process: inserting FFFE and toggling the 7th bit of the first octet from 0 to 1.

This H12-811 question tests the conversion of a MAC address to an IPv6 EUI-64 interface identifier. The correct answer is A, achieved by inserting FF-FE and flipping the U/L bit.

Common mistake: Candidates often select B by forgetting to invert the 7th bit, leaving the first byte as 00 instead of changing it to 02.

Expert Analysis

To derive the IPv6 address using the EUI-64 format from a given MAC address, two specific operations must be performed in sequence. First, the 48-bit MAC address is split into two 24-bit halves (the Organizationally Unique Identifier and the Extended Identifier). A 16-bit filler value of FFFE is inserted between these two halves. For the input MAC 00E0-FCEF-0FEC, splitting it yields 00E0-FC and EF-0FEC. Inserting FFFE results in the intermediate identifier: 00E0-FCFF-FEEF-0FEC.

Second, the Universal/Local bit (the 7th bit) of the first byte of the MAC address must be inverted. In standard IEEE 802 MAC addresses, this bit is typically set to '0' to indicate a globally unique address. In the EUI-64 format, this bit is flipped to '1' to distinguish it from other identifiers. The first byte of the MAC is 00 (hexadecimal), which is 0000 0000 in binary. Flipping the 7th bit (counting from left to right, starting at 1) changes the binary value to 0000 0010, which corresponds to hexadecimal 02. Applying this change to our intermediate string transforms the leading 00 into 02. The final resulting EUI-64 address is 02E0-FCFF-FEEF-0FEC.

The primary trap here involves neglecting the bit inversion or misinterpreting the insertion step. Comments discussing RADIUS or local authentication are irrelevant noise, likely due to mismatched question metadata in the source dump. However, the comment detailing the calculation correctly identifies that flipping the 7th bit and inserting FFFE leads to option A. Option B fails because it does not flip the bit. Option C fails because it inserts FFFE incorrectly (creating FCFF instead of keeping FC separate before insertion logic) or misses the bit flip while miscalculating the middle bytes. Option D keeps the original 00 prefix, ignoring the mandatory bit inversion.

Exam Strategy

When tackling EUI-64 conversion questions on certification exams, always perform the steps in order: split, insert, then flip. Write out the binary for the first byte explicitly if unsure; for example, 0x00 is 00000000, and flipping the 7th bit gives 00000010 (0x02). This prevents simple oversight errors that lead to distractors like leaving the prefix unchanged.

Frequently Asked Questions

Why is the 7th bit flipped in EUI-64?

The 7th bit is the Universal/Local (U/L) bit. It is flipped from 0 to 1 to indicate that the interface identifier is derived from a globally unique MAC address, distinguishing it from locally administered addresses.

What is the exact structure of an EUI-64 address?

An EUI-64 address is formed by taking the 48-bit MAC address, inserting 0xFFFE in the center, and inverting the 7th bit of the first octet. This creates a 64-bit interface identifier.

More H12-811 FAQ →

Community Votes

A
71%
C
29%

71% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 9 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 9

  1. NickENG 👍 3 Answered C
    Mac address is break in two blocks and in the middle you insert FFFE
  2. GaboK 👍 3 Answered A
    According to several calculators its 2e0:fcff:feef:fec, thus A
  3. surveycorps969 👍 2 Answered A
    Based on the explanation from the forum below, A is the correct answer. https://community.cisco.com/t5/switching/mac-to-eui-64-conversion/td-p/1432287
  4. akamg 👍 2 Answered A
    Option A is correct
  5. Godfather2022 👍 2
    Answer is C
Show 4 more comments
  1. hafizhou 👍 1
    B. Local. C. Radius. Explanation: B. Local: Refers to local authentication, where user credentials are stored locally on the router. C. Radius: Refers to authentication using a Remote Authentication Dial-In User Service (RADIUS) server. The router sends authentication requests to a RADIUS server, and the server validates the credentials. Option A (None) and Option D (802.1X$) are not accurate in the context of supported AAA authentication modes on Huawei AR G3 Series routers.
  2. Fmoura17 👍 1 Answered A
    A. 02E0-FCFF-FEEF-0FEC EUI-64 Conversion Steps: Step 1 — Split MAC in half and insert FF-FE in the middle: 00E0-FC | FF-FE | EF-0FEC = 00E0-FCFF-FEEF-0FEC Step 2 — Flip the 7th bit of the first byte: First byte: 00 = 0000 0000 Flip 7th bit: 0000 0010 = 02 Final Result: 02E0-FCFF-FEEF-0FEC
  3. Dafuerre 👍 1 Answered C
    Correct one is C. Mac address is break in two blocks and in the middle you insert FFFE
  4. Creyes1495 👍 1 Answered A
    Don't forget to change the 7th bit and assign FFFE in the middle.

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