Question 1,659 of 2,152

SNMP Troubleshooting →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the SNMP engine ID on the router changed after the NMS was configured, causing authentication failures for traps. This occurs because SNMPv3 binds the user’s authentication and privacy keys to the engine ID at the time of configuration; if the engine ID changes—due to a router reload, configuration replacement, or manual deletion—the NMS will reject the trap as it cannot decrypt or validate the credentials. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that SNMPv3 traps rely on a separate notification view and that the engine ID must remain consistent between the agent and the NMS for trap delivery, even when polling succeeds. A common trap is assuming that successful polling guarantees trap functionality, but polling uses the read view while traps use the notify view, and both depend on a stable engine ID. Memory tip: “Polling works, traps fail? Check the engine ID—it’s the key that binds the trap.”

300-410 SNMP Troubleshooting Practice Question

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

A network engineer configures SNMPv3 on a router with the 'snmp-server group' and 'snmp-server user' commands, using SHA for authentication and AES for privacy. The NMS can poll the router successfully, but SNMP traps are not received. Which is the most likely explanation?

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 1hardmultiple choice

Read the full network assurance explanation →

A
The SNMP engine ID on the router changed after the NMS was configured, causing authentication failures for traps.
The engine ID is used to derive keys; if it changes, the NMS cannot decrypt or authenticate traps, even though polling still works if the NMS uses the old engine ID.
B
The 'snmp-server enable traps' command was omitted, so no traps are generated.
Why wrong: This would prevent all traps, not just SNMPv3 traps, and polling would still work.
C
The NMS is using SNMPv2c for trap reception, which is incompatible with SNMPv3.
Why wrong: SNMPv3 traps can be received by an NMS that supports SNMPv3; the NMS must be configured for SNMPv3 traps.
D
The 'snmp-server host' command specifies a community string instead of the SNMPv3 username.
Why wrong: The 'snmp-server host' command for SNMPv3 requires the username, not a community string; using a community string would cause a configuration error, but polling would also fail.

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 SNMP engine ID on the router changed after the NMS was configured, causing authentication failures for traps.

SNMPv3 traps require that the engine ID be known to both the agent and the NMS. If the engine ID changes (e.g., due to a reload or configuration change), the NMS may not recognize the trap sender, causing traps to be dropped. Additionally, traps use a different notification view than the read view used for polling.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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 engine ID on the router changed after the NMS was configured, causing authentication failures for traps.
Why this is correct
The engine ID is used to derive keys; if it changes, the NMS cannot decrypt or authenticate traps, even though polling still works if the NMS uses the old engine ID.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The 'snmp-server enable traps' command was omitted, so no traps are generated.
Why it's wrong here
This would prevent all traps, not just SNMPv3 traps, and polling would still work.
✗
The NMS is using SNMPv2c for trap reception, which is incompatible with SNMPv3.
Why it's wrong here
SNMPv3 traps can be received by an NMS that supports SNMPv3; the NMS must be configured for SNMPv3 traps.
✗
The 'snmp-server host' command specifies a community string instead of the SNMPv3 username.
Why it's wrong here
The 'snmp-server host' command for SNMPv3 requires the username, not a community string; using a community string would cause a configuration error, but polling would also fail.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Trap categories for this question

Command / output trap
The 'snmp-server host' command for SNMPv3 requires the username, not a community string; using a community string would cause a configuration error, but polling would also fail.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Real-world example

How this comes up in practice

A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.

What to study next

Got this wrong? Here's your next step.

Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.

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FAQ

Questions learners often ask

What does this 300-410 question test?

SNMP Troubleshooting — This question tests SNMP Troubleshooting — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: The SNMP engine ID on the router changed after the NMS was configured, causing authentication failures for traps. — SNMPv3 traps require that the engine ID be known to both the agent and the NMS. If the engine ID changes (e.g., due to a reload or configuration change), the NMS may not recognize the trap sender, causing traps to be dropped. Additionally, traps use a different notification view than the read view used for polling.

What should I do if I get this 300-410 question wrong?

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?

Static NAT maps one inside address to one outside address.

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