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300-410 Practice Question: Is troubleshooting a router that is not…
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?
⚠ Common exam trap
Cisco often tests the distinction between reachability (ping working) and SNMP-specific filtering (ACL on community), leading candidates to incorrectly blame community string mismatch or SNMP version when the real issue is an access-list silently dropping SNMP packets.
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
✓
An ACL is applied to the SNMP community that denies the NMS IP.
The NMS can ping the router, confirming IP reachability, and 'show snmp' confirms SNMP is enabled. The most likely cause is an ACL applied to the SNMP community that denies the NMS IP address (10.1.1.100). Cisco IOS allows an access-list to be attached to an SNMP community string using the 'snmp-server community <string> [RO|RW] <acl-number>' command, which filters SNMP requests based on source IP. Since the NMS can ping but not poll, the ACL is blocking SNMP traffic while permitting ICMP.
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.
- ✗
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.