The answer is an ACL blocking the management station on the community string. Even though the router has `snmp-server community public RO` configured, if an access control list is implicitly or explicitly applied to that community string and does not permit the management station’s IP address, the router will silently drop SNMP polls while still allowing pings. This isolates the failure to SNMP-specific access control rather than Layer 3 connectivity, which is confirmed working by the successful ping. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that SNMP community strings can be locked down with an ACL, and the common trap is assuming a missing ACL means open access—in reality, an applied ACL that lacks a permit statement for the manager blocks all polls. Remember the memory tip: “Ping passes, SNMP fails? Check the ACL on the community string.”
300-410 Device Access Control Practice Question
This 300-410 practice question tests your understanding of device access control. 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 Cisco router that is not responding to SNMP polls from a management station. The router has 'snmp-server community public RO' configured. The management station 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.
The SNMP community string is not associated with an ACL that permits the management station.
Correct because without an ACL, the default behavior is to deny all SNMP access; the community must be bound to an ACL that permits the management station.
B
The SNMP version is not configured.
Why wrong: Incorrect because the 'snmp-server community' command enables SNMPv1/v2c by default.
C
The router's SNMP agent is disabled.
Why wrong: Incorrect because the 'snmp-server community' command enables the SNMP agent.
D
The management station is using the wrong SNMP port.
Why wrong: Incorrect because SNMP uses UDP port 161 by default, and the scenario does not indicate a port change.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The SNMP community string is not associated with an ACL that permits the management station.
The 'snmp-server community public RO' command configures an SNMP community string but does not restrict access by default. If no access control list (ACL) is associated with the community string, the router will respond to SNMP polls from any source. However, if an ACL is implicitly or explicitly applied that does not permit the management station's IP address, the router will silently drop the SNMP requests. Since the management station can ping the router, Layer 3 connectivity is confirmed, isolating the issue to SNMP-specific access control.
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 community string is not associated with an ACL that permits the management station.
Why this is correct
Correct because without an ACL, the default behavior is to deny all SNMP access; the community must be bound to an ACL that permits the management station.
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 version is not configured.
Why it's wrong here
Incorrect because the 'snmp-server community' command enables SNMPv1/v2c by default.
✗
The router's SNMP agent is disabled.
Why it's wrong here
Incorrect because the 'snmp-server community' command enables the SNMP agent.
✗
The management station is using the wrong SNMP port.
Why it's wrong here
Incorrect because SNMP uses UDP port 161 by default, and the scenario does not indicate a port change.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the nuance that an SNMP community string can have an implicit ACL (e.g., from a previous configuration or a default deny) that blocks management stations, leading candidates to overlook access control as the root cause when basic connectivity exists.
Trap categories for this question
Command / output trap
Incorrect because the 'snmp-server community' command enables SNMPv1/v2c by default.
Scenario analysis trap
Incorrect because SNMP uses UDP port 161 by default, and the scenario does not indicate a port change.
Detailed technical explanation
How to think about this question
When an ACL is applied to an SNMP community string via the 'snmp-server community <string> RO <acl-number>' command, the router's SNMP agent checks the source IP of incoming requests against the ACL before processing them. If the ACL denies the source, the agent silently discards the packet without sending a response, which is why the management station sees no reply despite successful ping. In real-world deployments, this is a common misconfiguration where an ACL is created but not correctly permitting the NMS IP, or the ACL is applied to the wrong community string.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Device Access Control — This question tests Device Access Control — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The SNMP community string is not associated with an ACL that permits the management station. — The 'snmp-server community public RO' command configures an SNMP community string but does not restrict access by default. If no access control list (ACL) is associated with the community string, the router will respond to SNMP polls from any source. However, if an ACL is implicitly or explicitly applied that does not permit the management station's IP address, the router will silently drop the SNMP requests. Since the management station can ping the router, Layer 3 connectivity is confirmed, isolating the issue to SNMP-specific access control.
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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