hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures SNMPv2c with a community…
An engineer configures SNMPv2c with a community string 'public' and an ACL that permits the NMS. The NMS can poll the router. The engineer then applies a CoPP policy that drops SNMP packets (UDP port 161) from all sources except the NMS. The NMS now fails to poll. Which is the most likely explanation?
⚠ Common exam trap
Cisco often tests the order of operations: CoPP is applied before the SNMP process, so a CoPP drop will prevent SNMP from ever seeing the packet, regardless of SNMP ACLs or community strings.
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 CoPP policy's ACL does not include the NMS IP address, so SNMP packets from the NMS are dropped by the class-default.
CoPP (Control Plane Policing) applies to all traffic destined to the router's control plane, including SNMP. If the CoPP policy's ACL does not explicitly permit the NMS IP address for UDP port 161, those packets fall into the class-default, which is configured to drop them. Even though the SNMP community string ACL permits the NMS, CoPP is evaluated before the packet reaches the SNMP process, so the drop occurs first.
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 CoPP policy's ACL does not include the NMS IP address, so SNMP packets from the NMS are dropped by the class-default.
Why this is correct
CoPP policies typically have a class that matches traffic to be permitted; if the NMS is not matched, its packets fall into class-default, which may be set to drop.
- ✗
CoPP only affects routing protocol traffic, not SNMP.
Why it's wrong here
CoPP can filter any control plane traffic, including SNMP.
- ✗
The SNMP community string ACL is overridden by the CoPP policy.
Why it's wrong here
The community string ACL and CoPP are independent; both must permit the traffic.
- ✗
The router requires a reload for the CoPP policy to take effect.
Why it's wrong here
CoPP policies are applied immediately.
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
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JA
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.