Question 209 of 2,152
SNMP TroubleshootingmediumMultiple ChoiceObjective-mapped

Troubleshooting SNMPv3 Authentication Failure Due to Missing ACL

This 300-410 practice question tests your understanding of snmp troubleshooting. 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.

A network engineer notices that an SNMPv3 poll from the NMS to router R1 fails with an authentication error. The engineer has configured 'snmp-server group ADMIN v3 priv' and 'snmp-server user admin ADMIN v3 auth sha cisco123 priv aes 128 cisco456'. The NMS is configured with the same credentials. What is the most likely cause of the failure?

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.

Quick Answer

The answer is a missing ACL on the SNMPv3 group configuration. Even when the username, authentication hash, and privacy protocol match perfectly between the NMS and the router, the `snmp-server group` command requires an `access` clause to explicitly permit the NMS IP address; without it, the router’s default behavior is to deny all SNMP requests, which manifests as an authentication failure in the logs. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that SNMPv3 authentication errors are not always credential mismatches—they often stem from access control restrictions, a common trap where engineers focus only on the user configuration. Remember the memory tip: “Group grants access, user grants identity”—if the group lacks an ACL, even a correctly authenticated user is locked out.

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 SNMP group is missing the 'access' ACL that permits the NMS IP address.

The group 'ADMIN' is configured with 'v3 priv', which requires both authentication and encryption. The user 'admin' is configured with 'auth sha cisco123 priv aes 128 cisco456', which includes both authentication and encryption. However, the 'priv' keyword in the group definition indicates that the group expects the privacy (encryption) passphrase. If the NMS is only sending the authentication credentials without the privacy passphrase, it will cause an authentication error because the group expects privacy but the NMS does not provide it. Changing the group to 'v3 auth' would align with the NMS's behavior, but the user is also configured for priv, so that would not be consistent. In this scenario, the most likely cause is that the NMS is not sending the privacy passphrase, leading to a mismatch. Option D correctly identifies that the group should be 'auth' to match the NMS's authentication-only attempt, even though the user configuration includes priv. Note: This is a nuanced scenario often tested in Cisco exams.

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.

  • The SNMP group is missing the 'access' ACL that permits the NMS IP address.

    Why this is correct

    Correct because SNMPv3 requires an access list on the group to allow the NMS; without it, the NMS is denied despite correct credentials.

    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 SNMP user password must be at least 8 characters; 'cisco123' is only 8, but the hash algorithm requires a minimum of 12 characters.

    Why it's wrong here

    Incorrect because SNMPv3 passwords do not have a minimum length of 12; 8 characters is acceptable for SHA.

  • The NMS is using SNMPv2c, which is incompatible with SNMPv3 configuration.

    Why it's wrong here

    Incorrect because the symptom is an authentication error, not a version mismatch; version mismatch would show a different error.

  • The 'priv' keyword in the group definition should be 'auth' instead to match the user's authentication settings.

    Why it's wrong here

    Incorrect because 'priv' in the group defines the security level; the user can have 'priv' even if the group is set to 'priv'.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Candidates often overlook the fact that the group security level must match the NMS's actual request. If the NMS only provides authentication credentials but the group requires privacy, the request fails with an authentication error, leading candidates to focus on password or ACL issues.

Trap categories for this question

  • Command / output trap

    Incorrect because the symptom is an authentication error, not a version mismatch; version mismatch would show a different error.

Detailed technical explanation

How to think about this question

In SNMPv3, the group defines the security model and access level (noAuthNoPriv, authNoPriv, or authPriv). The 'access' ACL on the group command filters which source IP addresses are allowed to use that group. Without an ACL, the group implicitly denies all SNMP requests, regardless of correct user credentials. This is a common misconfiguration because the ACL is optional but defaults to deny-all when omitted.

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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.

Quick reference

Symmetric Encryption Algorithm Comparison

AlgorithmKey SizeBlock SizeStatusNotes
AES-128128-bit128-bitCurrent standardNIST approved; WPA3, TLS
AES-256256-bit128-bitCurrent standardPreferred for sensitive / govt data
3DES112-bit effective64-bitDeprecated (2023)Replaced by AES
DES56-bit64-bitBrokenCracked in < 24 h; never deploy
ChaCha20256-bitStream cipherCurrentTLS 1.3, WireGuard

What to study next

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FAQ

Questions learners often ask

What does this 300-410 question test?

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

What is the correct answer to this question?

The correct answer is: The SNMP group is missing the 'access' ACL that permits the NMS IP address. — The group 'ADMIN' is configured with 'v3 priv', which requires both authentication and encryption. The user 'admin' is configured with 'auth sha cisco123 priv aes 128 cisco456', which includes both authentication and encryption. However, the 'priv' keyword in the group definition indicates that the group expects the privacy (encryption) passphrase. If the NMS is only sending the authentication credentials without the privacy passphrase, it will cause an authentication error because the group expects privacy but the NMS does not provide it. Changing the group to 'v3 auth' would align with the NMS's behavior, but the user is also configured for priv, so that would not be consistent. In this scenario, the most likely cause is that the NMS is not sending the privacy passphrase, leading to a mismatch. Option D correctly identifies that the group should be 'auth' to match the NMS's authentication-only attempt, even though the user configuration includes priv. Note: This is a nuanced scenario often tested in Cisco exams.

What should I do if I get this 300-410 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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Same concept, more angles

1 more ways this is tested on 300-410

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. snmp-server group MyGroup v3 priv\nsnmp-server user MyUser MyGroup v3 auth sha MyPassword priv aes 128 MyPrivKey What is missing from this SNMPv3 configuration?

medium
  • A.The group is missing a view definition to allow access to MIB objects.
  • B.The authentication protocol should be MD5 instead of SHA.
  • C.The privacy password must be at least 16 characters long.
  • D.The user must be configured under a different group name.

Why A: The configuration creates an SNMPv3 group 'MyGroup' with priv security level and a user 'MyUser' with SHA authentication and AES 128 privacy, but it does not include a view definition for the group. Without a view (e.g., via the 'snmp-server group MyGroup v3 priv view MyView' command or a default view), the group has no access to any MIB objects, rendering the SNMPv3 configuration non-functional for queries or notifications.

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Last reviewed: Jul 4, 2026

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