Question 293 of 500

Security →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the MACsec key chain must be created and explicitly referenced within the MACsec policy, and the MKA policy must be applied to the interface. Without the `key-chain` command under the `macsec policy`, the pre-shared key (CAK) is unavailable for the MACsec Key Agreement (MKA) protocol to derive session keys, causing MACsec frames to be dropped even though the feature and policy are enabled. This scenario tests your understanding of the complete MACsec pre-shared key configuration on Nexus 9000 switches, a common trap on the Cisco DCCOR 350-601 exam where candidates assume enabling the feature and policy alone is sufficient. The exam emphasizes that MKA requires both a defined key chain and a separate `macsec mka policy` applied to the interface to negotiate secure connectivity. Remember the mnemonic: **Key Chain + MKA Policy = Secure Link**; missing either breaks the MACsec handshake.

350-601 Security Practice Question

This 350-601 practice question tests your understanding of security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

Two Cisco Nexus 9000 switches are connected via Ethernet interface 1/1. The engineer wishes to secure the link using MACsec (IEEE 802.1ae) with a pre-shared key for connectivity association key (CAK) protection. Both switches have the same hardware and software version supporting MACsec. The engineer configures the following on both switches:

feature macsec macsec policy MACSEC_POLICY cipher-suite gcm-aes-128 security-mode no-encrypt mka sak-rekey-time 30

interface ethernet 1/1

macsec policy MACSEC_POLICY

However, the link comes up without MACsec encryption (the port counter shows MACsec frames dropped). The engineer checks that the pre-shared key is configured correctly via 'macsec key-chain' but notices it was not explicitly applied. What is the most likely reason for MACsec failing to establish?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1mediummultiple choice

Full question →

A
Both switches must have the same MACsec profile name.
Why wrong: The policy name can be different as long as the parameters match; but the missing key is the issue.
B
The interface must be put in a 'macsec' mode with 'switchport macsec'.
Why wrong: On Nexus 9000, 'macsec policy' is applied directly to the interface; no separate 'switchport macsec' command.
C
The MACsec key chain must be created and referenced in the macsec policy, and the MKA policy must be applied to the interface with 'macsec mka policy'.
Correct. A key chain must be defined and linked to the policy, and the MKA policy must be explicitly applied under the interface.
D
The 'feature macsec' command is not enabled, so MACsec is not operational.
Why wrong: It is enabled in the config snippet.

Full breakdown with real-world context →

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

✓

The MACsec key chain must be created and referenced in the macsec policy, and the MKA policy must be applied to the interface with 'macsec mka policy'.

Option C is correct because MACsec on Cisco Nexus 9000 switches requires a key chain to be defined and explicitly referenced within the MACsec policy. Without the 'key-chain' command under the 'macsec policy', the pre-shared key (CAK) is not available for MKA (MACsec Key Agreement) to derive session keys. Additionally, the MKA policy must be applied to the interface using 'macsec mka policy' to enable the key agreement protocol; simply enabling MACsec on the interface without these steps leaves the link unsecured, causing MACsec frames to be dropped.

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.

✗
Both switches must have the same MACsec profile name.
Why it's wrong here
The policy name can be different as long as the parameters match; but the missing key is the issue.
✗
The interface must be put in a 'macsec' mode with 'switchport macsec'.
Why it's wrong here
On Nexus 9000, 'macsec policy' is applied directly to the interface; no separate 'switchport macsec' command.
✓
The MACsec key chain must be created and referenced in the macsec policy, and the MKA policy must be applied to the interface with 'macsec mka policy'.
Why this is correct
Correct. A key chain must be defined and linked to the policy, and the MKA policy must be explicitly applied under the interface.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The 'feature macsec' command is not enabled, so MACsec is not operational.
Why it's wrong here
It is enabled in the config snippet.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the requirement that a key chain must be explicitly referenced in the MACsec policy and that an MKA policy must be applied to the interface, tricking candidates into thinking that simply enabling MACsec on the interface with a policy is sufficient.

Trap categories for this question

Command / output trap
On Nexus 9000, 'macsec policy' is applied directly to the interface; no separate 'switchport macsec' command.

Detailed technical explanation

How to think about this question

MACsec (IEEE 802.1ae) relies on MKA (IEEE 802.1X-2010) to authenticate peers and distribute session keys. The CAK (Connectivity Association Key) is stored in a key chain and referenced by the MACsec policy; without this, MKA cannot establish a secure channel. The 'security-mode no-encrypt' option enables integrity-only protection (using GCM-AES-128 for ICV), which still requires the key to be present. In real-world deployments, misconfiguring the key chain or forgetting to apply the MKA policy is a common pitfall that results in MACsec frames being dropped at the receiver.

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.

TExam Day Tips

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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this 350-601 question test?

Security — This question tests Security — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The MACsec key chain must be created and referenced in the macsec policy, and the MKA policy must be applied to the interface with 'macsec mka policy'. — Option C is correct because MACsec on Cisco Nexus 9000 switches requires a key chain to be defined and explicitly referenced within the MACsec policy. Without the 'key-chain' command under the 'macsec policy', the pre-shared key (CAK) is not available for MKA (MACsec Key Agreement) to derive session keys. Additionally, the MKA policy must be applied to the interface using 'macsec mka policy' to enable the key agreement protocol; simply enabling MACsec on the interface without these steps leaves the link unsecured, causing MACsec frames to be dropped.

What should I do if I get this 350-601 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 24, 2026

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