The answer is an ACL applied to the SNMP community that denies the NMS IP. This is correct because even when SNMP communities like "public" and "private" are configured and the router responds to pings, an access-list attached to the community string can silently drop SNMP requests from unauthorized sources, causing the poll to fail while leaving other connectivity intact. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of SNMP security features and the common misconfiguration where an ACL is applied to a community without permitting the NMS IP—a frequent trap because engineers often check basic SNMP enablement and reachability first. Remember that a successful ping only confirms IP connectivity, not SNMP access; the ACL acts as a filter at the application layer. Memory tip: "Ping works, SNMP doesn't? Check the community ACL—it's the silent gatekeeper."
300-410 Device Management Practice Question
This 300-410 practice question tests your understanding of device management. 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 a router that is not responding to SNMP polls from the NMS at 10.1.1.100. The SNMP configuration includes 'snmp-server community public RO' and 'snmp-server community private RW'. The engineer can ping the router from the NMS. 'show snmp' shows SNMP is enabled. 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.
Why wrong: The router supports SNMPv2c by default; if the NMS uses SNMPv1, it would still work with the community string. Version mismatch is less common than ACL filtering.
B
An ACL is applied to the SNMP community that denies the NMS IP.
The configuration may include 'snmp-server community public RO 10', where ACL 10 denies the NMS; this is a common misconfiguration.
C
The router's SNMP agent is disabled due to high CPU.
Why wrong: High CPU would not disable SNMP; the agent would still respond, albeit slowly.
D
The NMS is using the wrong community string.
Why wrong: While possible, the engineer has verified the configuration; the community strings are correct, so the issue is likely access control.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
An ACL is applied to the SNMP community that denies the NMS IP.
The router has SNMP communities configured, but an ACL may be applied to the community that restricts access. The most common issue is an access-list applied to the community string that does not permit the NMS IP.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 using the wrong SNMP version.
Why it's wrong here
The router supports SNMPv2c by default; if the NMS uses SNMPv1, it would still work with the community string. Version mismatch is less common than ACL filtering.
✓
An ACL is applied to the SNMP community that denies the NMS IP.
Why this is correct
The configuration may include 'snmp-server community public RO 10', where ACL 10 denies the NMS; this is a common misconfiguration.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The router's SNMP agent is disabled due to high CPU.
Why it's wrong here
High CPU would not disable SNMP; the agent would still respond, albeit slowly.
✗
The NMS is using the wrong community string.
Why it's wrong here
While possible, the engineer has verified the configuration; the community strings are correct, so the issue is likely access control.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.
Device Management — This question tests Device Management — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: An ACL is applied to the SNMP community that denies the NMS IP. — The router has SNMP communities configured, but an ACL may be applied to the community that restricts access. The most common issue is an access-list applied to the community string that does not permit the NMS IP.
What should I do if I get this 300-410 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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