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300-410 Practice Question: Is troubleshooting why the NMS cannot poll SNMP…
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?
⚠ Common exam trap
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.
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.
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.
- ✗
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.
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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.