Question 1,045 of 1,819
Network Infrastructure and ConnectivityhardConfigurationObjective-mapped

How to Calculate IPv6 EUI-64 Address from MAC Address

This 200-301 practice question tests your understanding of network infrastructure and connectivity. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Network Topology
G0/0192.168.1.1/24R1SW1

You are connected to the console of R1. The network uses IPv6 with EUI-64. R1's GigabitEthernet0/0 has MAC address 0011.2233.4455. You need to configure an IPv6 global unicast address on this interface using EUI-64 format, based on the prefix 2001:db8:acad:1::/64. The interface is currently configured with an IPv4 address only.

Quick Answer

The correct answer is to configure the interface with the command ipv6 address 2001:db8:acad:1:0211:22ff:fe33:4455/64. This is because to calculate an IPv6 EUI-64 address from a MAC address, you split the 48-bit MAC 0011.2233.4455 into two 24-bit halves, insert FFFE in the middle to get 0011.22FF.FE33.4455, and then flip the seventh bit (the Universal/Local bit) of the first octet from 0 to 1, changing 00 to 02, yielding the interface identifier 0211:22ff:fe33:4455. On the CCNA 200-301 v2 exam, this topic tests your understanding of IPv6 address autoconfiguration and the EUI-64 process, often appearing in configuration or drag-and-drop questions where you must derive the full address. A common trap is forgetting to flip the U/L bit or misplacing the FF:FE insertion, so always double-check the first octet. Memory tip: think "FF:FE in the middle, then flip the seventh bit to make it globally unique."

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

R1(config-if)# ipv6 address 2001:db8:acad:1:0211:22ff:fe33:4455/64

The EUI-64 process splits the MAC address 0011.2233.4455 into two halves: 0011.22 and 33.4455. It inserts FFFE in between to get 0011.22FFFE33.4455, then flips the seventh bit (U/L bit) of the first byte from 00 to 02, resulting in 0211.22FF.FE33.4455. The full IPv6 address is 2001:db8:acad:1:0211:22ff:fe33:4455/64. Option A correctly uses this manually computed address. Options B and C have incorrect interface IDs. Option D uses the 'eui-64' keyword which automatically derives the interface ID from the MAC, but the question expects the static address, as indicated by the provided options. Therefore, option A is the correct answer.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • R1(config-if)# ipv6 address 2001:db8:acad:1:0211:22ff:fe33:4455/64

    Why this is correct

    Correct. This command manually configures the EUI-64-derived address after flipping the U/L bit.

    Related concept

    Read the scenario before looking for a memorised answer.

  • R1(config-if)# ipv6 address 2001:db8:acad:1:0011:22ff:fe33:4455/64

    Why it's wrong here

    Incorrect. The interface ID uses 0011 instead of 0211; the seventh bit must be flipped.

  • R1(config-if)# ipv6 address 2001:db8:acad:1:0211:2233:4455:5566/64

    Why it's wrong here

    Incorrect. The interface ID is completely wrong; it does not follow EUI-64 from the given MAC.

  • R1(config-if)# ipv6 address 2001:db8:acad:1::/64 eui-64

    Why it's wrong here

    Incorrect. Although 'ipv6 address ... eui-64' is a valid Cisco IOS command that automatically derives the interface ID from the MAC, the question expects the manually computed static address as shown in option A.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

R1(config-if)# ipv6 address 2001:db8:acad:1:0211:22ff:fe33:4455/64Correct answer

Why this is correct

Correct. This command manually configures the EUI-64-derived address after flipping the U/L bit.

R1(config-if)# ipv6 address 2001:db8:acad:1:0011:22ff:fe33:4455/64Wrong answer — click to see why

Why this is wrong here

The specific factual error is that the U/L bit was not flipped. The EUI-64 process requires flipping the seventh bit of the first byte of the MAC address.

Why candidates choose this

Candidates may forget to flip the U/L bit, as it is a common step that is easy to overlook. They might think the MAC address is simply inserted with FF:FE without modification.

R1(config-if)# ipv6 address 2001:db8:acad:1:0211:2233:4455:5566/64Wrong answer — click to see why

Why this is wrong here

The specific factual error is that FF:FE was not inserted between the first and second halves of the MAC address. The EUI-64 format requires the insertion of FF:FE.

Why candidates choose this

Candidates might confuse EUI-64 with simply using the MAC address directly or with other address generation methods. They may also misremember the insertion point or the format.

R1(config-if)# ipv6 address 2001:db8:acad:1::/64 eui-64Wrong answer — click to see why

Why this is wrong here

The specific factual error is that the question asks for the resulting IPv6 address, not the configuration command. The command 'ipv6 address ... eui-64' is used to enable EUI-64, but the answer should be the actual address.

Why candidates choose this

Candidates might think the question is asking for the command to configure EUI-64, as that is a common configuration task. They may not read the question carefully and provide the command instead of the address.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

Common exam traps

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Trap categories for this question

  • Command / output trap

    Incorrect. Although 'ipv6 address ... eui-64' is a valid Cisco IOS command that automatically derives the interface ID from the MAC, the question expects the manually computed static address as shown in option A.

Detailed technical explanation

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.
  • Use explanations to understand the rule behind the answer.

TExam Day Tips

  • Underline the problem statement mentally.
  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

Quick reference

Access Control Model Comparison

ModelAcronymWho Controls Access?Best For
Discretionary Access ControlDACResource ownerSmall teams, file shares
Mandatory Access ControlMACSystem / security labelsClassified govt / military
Role-Based Access ControlRBACAdministrator (via roles)Enterprise environments
Attribute-Based Access ControlABACPolicy engine (user + resource attributes)Fine-grained, dynamic policies
Rule-Based Access ControlRuBACSystem rules / ACLsFirewall rules, network ACLs

What to study next

Got this wrong? Here's your next step.

Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

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FAQ

Questions learners often ask

What does this 200-301 question test?

Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: R1(config-if)# ipv6 address 2001:db8:acad:1:0211:22ff:fe33:4455/64 — The EUI-64 process splits the MAC address 0011.2233.4455 into two halves: 0011.22 and 33.4455. It inserts FFFE in between to get 0011.22FFFE33.4455, then flips the seventh bit (U/L bit) of the first byte from 00 to 02, resulting in 0211.22FF.FE33.4455. The full IPv6 address is 2001:db8:acad:1:0211:22ff:fe33:4455/64. Option A correctly uses this manually computed address. Options B and C have incorrect interface IDs. Option D uses the 'eui-64' keyword which automatically derives the interface ID from the MAC, but the question expects the static address, as indicated by the provided options. Therefore, option A is the correct answer.

What should I do if I get this 200-301 question wrong?

Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 7, 2026

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