Question 1,430 of 2,152

SNMP Troubleshooting →hardMultiple ChoiceObjective-mapped

Why ACL on SNMP Community String Breaks NMS Access

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 is troubleshooting why the NMS cannot poll SNMP data from router R5. The router has 'snmp-server community cisco RO' configured. The NMS is on subnet 192.168.1.0/24, and the router has an ACL applied to the VTY lines that permits only 10.0.0.0/8. The NMS can ping the router. What is the most likely cause?

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 engineer applied an ACL to the SNMP community that denies the NMS subnet, but the VTY ACL is unrelated.
Correct because the community string's ACL must permit the NMS; the VTY ACL does not affect SNMP.
B
The VTY ACL is blocking SNMP packets because SNMP uses TCP port 161.
Why wrong: Incorrect because SNMP uses UDP port 161, not TCP, and VTY ACLs only affect Telnet/SSH.
C
The router needs the 'snmp-server ifindex persist' command to enable polling.
Why wrong: Incorrect because ifindex persist is for interface indexing, not for basic polling.
D
The NMS is using SNMPv3, but the router only has SNMPv2c configured.
Why wrong: Incorrect because the router has an SNMPv2c community; if the NMS uses v3, it would need a user configuration.

Full breakdown with real-world context →

Quick Answer

The answer is that an ACL applied to the SNMP community string is blocking the NMS subnet, while the VTY ACL is a red herring. SNMP access is governed solely by the optional access-list referenced in the `snmp-server community` command, not by VTY line ACLs, which only control SSH and Telnet sessions. On the Cisco CCNP ENARSI 300-410 exam, this question tests your ability to distinguish between management-plane access controls—a common trap where engineers mistakenly blame VTY restrictions for SNMP failures. If the community string lacks an ACL, SNMP defaults to permitting all sources, so the symptom of a blocked poll despite a successful ping points directly to an ACL on the community string that denies the NMS’s subnet. Memory tip: “VTY for TTY, SNMP for the community ACL—don’t mix your management planes.”

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 engineer applied an ACL to the SNMP community that denies the NMS subnet, but the VTY ACL is unrelated.

The NMS can ping the router, confirming IP connectivity, but it cannot poll SNMP data. The VTY ACL only controls Telnet/SSH access to the router's VTY lines, not SNMP traffic, which uses UDP port 161. The most likely cause is that an ACL has been applied directly to the SNMP community string (via the `snmp-server community cisco RO <acl-number>` command) that denies the NMS subnet 192.168.1.0/24, blocking SNMP polling while leaving ping and VTY access unaffected.

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 engineer applied an ACL to the SNMP community that denies the NMS subnet, but the VTY ACL is unrelated.
Why this is correct
Correct because the community string's ACL must permit the NMS; the VTY ACL does not affect SNMP.
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 VTY ACL is blocking SNMP packets because SNMP uses TCP port 161.
Why it's wrong here
Incorrect because SNMP uses UDP port 161, not TCP, and VTY ACLs only affect Telnet/SSH.
✗
The router needs the 'snmp-server ifindex persist' command to enable polling.
Why it's wrong here
Incorrect because ifindex persist is for interface indexing, not for basic polling.
✗
The NMS is using SNMPv3, but the router only has SNMPv2c configured.
Why it's wrong here
Incorrect because the router has an SNMPv2c community; if the NMS uses v3, it would need a user configuration.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that VTY ACLs control all management plane traffic, including SNMP, when in fact VTY ACLs only apply to Telnet/SSH sessions, and SNMP is controlled by ACLs applied directly to the community string or via SNMP views.

Detailed technical explanation

How to think about this question

SNMP community-based ACLs are applied using the `snmp-server community <string> RO <acl-number>` command, which filters SNMP requests at the router's SNMP agent level before any processing occurs. This is independent of VTY ACLs, which are applied to inbound TCP connections on lines 0-4/15. In real-world deployments, engineers often misapply VTY ACLs thinking they control all management traffic, but SNMP uses UDP and bypasses VTY entirely; the correct approach is to apply a dedicated ACL to the SNMP community string or use SNMPv3 with encryption and authentication.

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.

Related 300-410 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

Layer 3 Technologies practice questions

Practise 300-410 questions linked to Layer 3 Technologies.

EIGRP Troubleshooting practice questions

Practise 300-410 questions linked to EIGRP Troubleshooting.

OSPF Troubleshooting (v2/v3) practice questions

Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).

BGP Troubleshooting practice questions

Practise 300-410 questions linked to BGP Troubleshooting.

Route Redistribution practice questions

Practise 300-410 questions linked to Route Redistribution.

Policy-Based Routing (PBR) practice questions

Practise 300-410 questions linked to Policy-Based Routing (PBR).

VRF-Lite practice questions

Practise 300-410 questions linked to VRF-Lite.

Route Maps and Route Filtering practice questions

Practise 300-410 questions linked to Route Maps and Route Filtering.

Administrative Distance practice questions

Practise 300-410 questions linked to Administrative Distance.

Route Summarization practice questions

Practise 300-410 questions linked to Route Summarization.

Bidirectional Forwarding Detection (BFD) practice questions

Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).

VPN Technologies practice questions

Practise 300-410 questions linked to VPN Technologies.

Practice this exam

Start a free 300-410 practice session

Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.

10 questions 20 questions 30 questions 50 questions Timed 30

300-410 practice-test guide →Study guide →Browse all practice tests

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 engineer applied an ACL to the SNMP community that denies the NMS subnet, but the VTY ACL is unrelated. — The NMS can ping the router, confirming IP connectivity, but it cannot poll SNMP data. The VTY ACL only controls Telnet/SSH access to the router's VTY lines, not SNMP traffic, which uses UDP port 161. The most likely cause is that an ACL has been applied directly to the SNMP community string (via the `snmp-server community cisco RO <acl-number>` command) that denies the NMS subnet 192.168.1.0/24, blocking SNMP polling while leaving ping and VTY access unaffected.

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.

About these practice questions

Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →

How Courseiva writes practice questions · Editorial policy

Keep practising

Question Discussion

Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.

Loading comments…

This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.