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300-410 Practice Question: An engineer is troubleshooting why the NMS is not…
An engineer is troubleshooting why the NMS is not receiving SNMP traps from router R2. The configuration includes 'snmp-server enable traps', 'snmp-server host 10.1.1.100 version 2c public', and an extended ACL 100 that permits UDP port 162 from 10.1.1.100. The NMS can ping R2. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the distinction between inbound and outbound ACL application, and candidates mistakenly think an inbound ACL can filter locally generated traffic like SNMP traps, when in fact only outbound ACLs affect traffic leaving the router.
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 ACL is applied inbound on the interface, but it should be applied outbound to allow trap packets to leave the router.
The most likely cause is that the ACL is applied inbound on the interface, but it should be applied outbound to allow trap packets to leave the router. SNMP traps are UDP packets sourced from the router (typically from a random high port) and destined to the NMS at UDP port 162. An inbound ACL filters traffic entering the interface, not leaving it, so it would not affect outgoing trap packets. Applying the ACL outbound would permit the trap traffic to exit the router and reach the NMS.
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 ACL is applied inbound on the interface, but it should be applied outbound to allow trap packets to leave the router.
Why this is correct
Correct because traps are sent from the router; the ACL must permit outbound UDP port 162 to the NMS, not inbound.
- ✗
The 'snmp-server host' command is missing the 'trap' keyword, causing the router to send informs instead.
Why it's wrong here
Incorrect because 'snmp-server host' defaults to traps; no keyword is needed.
- ✗
The community string 'public' is case-sensitive; the NMS is using 'Public' with a capital P.
Why it's wrong here
Incorrect because case sensitivity would cause authentication failure, but the NMS can ping, and the issue is likely ACL-related.
- ✗
The router needs the 'snmp-server trap-source' command to specify the source interface for traps.
Why it's wrong here
Incorrect because while trap-source can help, it is not required; the default source IP is the outgoing interface IP.
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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.