Question 1,683 of 2,152

SNMP Troubleshooting →hardMultiple ChoiceObjective-mapped

Troubleshooting SNMP Traps Sourced from Loopback

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 with authentication and privacy on a router. The NMS polls the router via the management interface. The engineer then adds a loopback interface and configures the router to send SNMP traps sourced from the loopback IP. The NMS stops receiving traps. 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.

A
The NMS is configured to accept traps only from the management interface IP address, not the loopback IP.
NMS trap receivers often filter or authenticate based on source IP; if the source IP changes, traps may be dropped.
B
The loopback interface does not support SNMP trap generation.
Why wrong: Traps can be sourced from any interface.
C
The SNMP engine ID changed when the loopback interface was added.
Why wrong: Adding a loopback does not change the engine ID.
D
The 'snmp-server trap-source' command requires a specific interface type.
Why wrong: The command accepts any interface.

Full breakdown with real-world context →

Quick Answer

The answer is that the NMS is configured to accept traps only from the management interface IP address, not the loopback IP. This is correct because when you configure an SNMP trap source loopback, the router changes the source IP of the trap packet to the loopback address, which the NMS may not recognize as an authorized sender if its trap receiver is locked to the original management IP. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding of SNMP trap source behavior and NMS filtering—a common pitfall when troubleshooting SNMP trap source loopback not received scenarios. The key concept is that the NMS often performs source-based validation, so changing the trap source without updating the NMS breaks trap delivery. Memory tip: “Source mismatch sinks the trap”—always verify that the NMS’s allowed sender list matches the configured trap source IP.

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 NMS is configured to accept traps only from the management interface IP address, not the loopback IP.

Option A is correct because the NMS is likely configured with an ACL or trap receiver filter that only accepts SNMP traps from the management interface IP address. When the engineer configures 'snmp-server trap-source loopback0', the router changes the source IP of all outgoing traps to the loopback IP. If the NMS is not expecting traps from that IP, it will drop them, even though SNMPv3 authentication and privacy are correctly configured.

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 NMS is configured to accept traps only from the management interface IP address, not the loopback IP.
Why this is correct
NMS trap receivers often filter or authenticate based on source IP; if the source IP changes, traps may be dropped.
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 loopback interface does not support SNMP trap generation.
Why it's wrong here
Traps can be sourced from any interface.
✗
The SNMP engine ID changed when the loopback interface was added.
Why it's wrong here
Adding a loopback does not change the engine ID.
✗
The 'snmp-server trap-source' command requires a specific interface type.
Why it's wrong here
The command accepts any interface.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that SNMPv3 security (auth/priv) is the cause of trap delivery failure, when in fact the issue is a source IP mismatch due to the 'snmp-server trap-source' command overriding the default source address.

Trap categories for this question

Command / output trap
The command accepts any interface.

Detailed technical explanation

How to think about this question

Under the hood, SNMP traps are UDP packets sent from the router to the NMS. The source IP address is determined by the routing table or explicitly set via 'snmp-server trap-source'. If the NMS uses an ACL to permit only specific source IPs (e.g., the management interface IP), traps sourced from a different IP will be silently dropped. In real-world deployments, this is a common misconfiguration when adding redundant paths or loopbacks for trap sourcing without updating NMS filters.

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.

Visual reference

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 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 NMS is configured to accept traps only from the management interface IP address, not the loopback IP. — Option A is correct because the NMS is likely configured with an ACL or trap receiver filter that only accepts SNMP traps from the management interface IP address. When the engineer configures 'snmp-server trap-source loopback0', the router changes the source IP of all outgoing traps to the loopback IP. If the NMS is not expecting traps from that IP, it will drop them, even though SNMPv3 authentication and privacy are correctly configured.

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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