CCNA Network Services and Security Practice Question
A network engineer notices that an NMS at 10.1.1.200 cannot poll a router that has SNMPv2c configured with community string 'public'. What is causing this issue?
⚠ Common exam trap
Cisco often tests the misconception that SNMP community strings are the only authentication mechanism, leading candidates to overlook the ACL restriction that can silently block polling from specific hosts.
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 SNMP community 'public' has an access list that only permits host 10.1.1.100.
SNMPv2c community strings can be restricted by an access control list (ACL) that specifies which source IP addresses are allowed to poll the router. If the ACL only permits host 10.1.1.100, then the NMS at 10.1.1.200 will be denied access even though the community string 'public' is correct. This is a common configuration for security, but it prevents polling from unauthorized hosts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
SNMPv2c is not enabled on the router.
Why it's wrong here
Configuring the SNMP community string 'public' via the snmp-server community command implicitly enables the SNMP agent for SNMPv1 and SNMPv2c on the router; no separate 'enable' command is required. Because the question states the community string is configured, the SNMPv2c agent is active and listening, so a lack of enablement cannot be the cause of the NMS's failed polls. The issue must instead lie in how the community is restricted, not in whether the agent version is enabled.
- ✓
The SNMP community 'public' has an access list that only permits host 10.1.1.100.
Why this is correct
The community string 'public' has an access control list applied that restricts source addresses to 10.1.1.100 only. When the NMS at 10.1.1.200 sends an SNMP poll, the router checks the source IP against the ACL bound to the community string; because 10.1.1.200 is not permitted, the router silently discards the request. This explains why the NMS receives no response, even though the community string matches and the SNMP agent is running.
- ✗
The NMS is using the wrong community string.
Why it's wrong here
The NMS is not using the wrong community string; both the router and the NMS have been configured with 'public' as the SNMP community. A community string mismatch would cause the router to drop the request with an authentication failure, but the scenario explicitly states that the community is correctly set. Therefore, the failure must be caused by a filtering mechanism, such as an ACL applied to the community, rather than a mismatch.
- ✗
The router's SNMP agent is not listening on the interface facing 10.1.1.200.
Why it's wrong here
By default, the Cisco IOS SNMP agent listens on all IP interfaces and does not restrict its operation to a specific interface unless configured with the snmp-server interface command. The problem statement does not indicate any interface-specific SNMP configuration, so the agent is reachable on the interface facing 10.1.1.200. Since the agent is listening globally, this option cannot explain why the NMS at 10.1.1.200 gets no response while 10.1.1.100 would succeed.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The SNMP community 'public' has an access list that only permits host 10.1.1.100.Correct answer▾
Why this is correct
The community string 'public' has an access control list applied that restricts source addresses to 10.1.1.100 only. When the NMS at 10.1.1.200 sends an SNMP poll, the router checks the source IP against the ACL bound to the community string; because 10.1.1.200 is not permitted, the router silently discards the request. This explains why the NMS receives no response, even though the community string matches and the SNMP agent is running.
✗SNMPv2c is not enabled on the router.Wrong answer — click to see why▾
Why this is wrong here
Many believe SNMP requires an additional global command to start; on Cisco IOS, a community string entry enables the agent.
✗The NMS is using the wrong community string.Wrong answer — click to see why▾
Why this is wrong here
Polling failures are often attributed to community string errors, but when the string matches, an ACL restriction produces identical symptoms.
✗The router's SNMP agent is not listening on the interface facing 10.1.1.200.Wrong answer — click to see why▾
Why this is wrong here
Candidates may assume the agent must be bound to an interface, but Cisco IOS SNMP agents respond on any interface unless limited by an ACL or VRF.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Go deeper
Related to this question
Learn chapter
RA Guard — IPv6 First-Hop Security
Key term
SNMP
SNMP (Simple Network Management Protocol) is an application-layer protocol used to collect and organize information about managed devices on IP networks and to modify that information to change device behavior.
Key term
Access Control List
An Access Control List is a set of rules that decides which traffic is allowed or denied entry to a network or device.
About these practice questions
Courseiva writes every 200-301 question from scratch — 1,389 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.