- A
An ACL is applied to the SNMP community string that does not permit the NMS IP address.
The snmp-server community command can have an optional ACL. If configured, it filters SNMP access. The debug shows ACL violation, so this is the direct cause.
- B
OSPF network type mismatch between R1 and R2 causes routing blackhole.
Why wrong: OSPF network type mismatch can cause adjacency issues, but the symptom is SNMP polling failure, not routing loss. Debug shows ACL violation, not routing.
- C
The NMS is using SNMPv3 with incorrect credentials, causing authentication failure.
Why wrong: The debug shows 'access-list violation', not authentication failure. SNMPv3 authentication would show different debug messages.
- D
R2's loopback interface is not advertised into OSPF, making it unreachable.
Why wrong: If the loopback were not advertised, the NMS would not have a route, but the debug shows packets reaching R2 and being dropped by ACL, so routing is working.
Root Cause Analysis of Intermittent SNMP Polling Failures
This 300-410 practice question tests your understanding of snmp troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A large enterprise network is experiencing intermittent SNMP polling failures from the NMS to router R2. R1 and R2 are connected via a serial link running OSPF. R1 has the following relevant configuration: snmp-server community public RO, snmp-server community private RW, snmp-server trap-source Loopback0, snmp-server enable traps ospf. R2 shows: debug ip packet shows packets from NMS (10.1.1.100) to R2's Loopback0 (10.2.2.2) being dropped with 'access-list violation'. No ACL is applied to any interface on R2. What is the root cause?
Quick Answer
The answer is an ACL applied to the SNMP community string that does not permit the NMS IP address. This is correct because the debug output on R2 explicitly shows packets being dropped with an "access-list violation," yet no ACL is applied to any interface. When an SNMP community string is configured with an optional ACL, that ACL filters incoming SNMP requests at the application layer before the router processes them; if the NMS IP is not permitted, the router silently drops the packets, mimicking an interface ACL violation. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to differentiate between interface ACLs, CoPP policies, and SNMP community ACLs during root cause analysis of intermittent SNMP polling failures. A common trap is to assume a missing interface ACL means no filtering exists, but SNMP community ACLs operate independently. Memory tip: "SNMP community ACLs are invisible gatekeepers—if the NMS can't ping but debug shows ACL drops, check the community string's access-list first."
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 string that does not permit the NMS IP address.
The debug output on R2 shows packets from the NMS (10.1.1.100) to R2's Loopback0 (10.2.2.2) being dropped with 'access-list violation'. Since no ACL is applied to any interface on R2, the only remaining ACL that could cause this is an SNMP community ACL. The SNMP community string 'public' or 'private' can have an optional ACL applied via the 'snmp-server community <string> [view <view-name>] [ro|rw] [acl-number]' command. If that ACL does not permit the NMS IP address (10.1.1.100), the router will silently drop SNMP packets from that source, even though no interface ACL exists. This matches the symptom exactly.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
An ACL is applied to the SNMP community string that does not permit the NMS IP address.
- ✗
OSPF network type mismatch between R1 and R2 causes routing blackhole.
- ✗
The NMS is using SNMPv3 with incorrect credentials, causing authentication failure.
Why it's wrong here
The debug shows 'access-list violation', not authentication failure. SNMPv3 authentication would show different debug messages.
- ✗
R2's loopback interface is not advertised into OSPF, making it unreachable.
Why it's wrong here
If the loopback were not advertised, the NMS would not have a route, but the debug shows packets reaching R2 and being dropped by ACL, so routing is working.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the concept that ACLs can be applied to SNMP community strings (not just interfaces), and candidates mistakenly assume 'no ACL on interfaces' means no ACL is dropping traffic, overlooking the community-string-level ACL as the root cause.
Trap categories for this question
Command / output trap
OSPF network type mismatch can cause adjacency issues, but the symptom is SNMP polling failure, not routing loss. Debug shows ACL violation, not routing.
Detailed technical explanation
How to think about this question
SNMP community ACLs are applied directly to the community string, not to an interface, and are evaluated before any SNMP processing occurs. The 'access-list violation' debug message is generated by the router's IP stack when an incoming packet matches a deny entry in any ACL, including those referenced by the 'snmp-server community' command. In real-world scenarios, this is a common misconfiguration when administrators copy SNMP configurations between devices without adjusting the ACL to include the correct NMS source IP, leading to silent polling failures that are difficult to trace without enabling debug ip packet.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
SNMP Troubleshooting — study guide chapter
Learn the concepts, then practise the questions
- →
SNMP Troubleshooting practice questions
Targeted practice on this topic area only
- →
All 300-410 questions
2,152 questions across all exam domains
- →
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
- →
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 300-410 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Layer 3 Technologies practice questions
Practise 300-410 questions linked to Layer 3 Technologies.
EIGRP Troubleshooting practice questions
Practise 300-410 questions linked to EIGRP Troubleshooting.
OSPF Troubleshooting (v2/v3) practice questions
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
BGP Troubleshooting practice questions
Practise 300-410 questions linked to BGP Troubleshooting.
Route Redistribution practice questions
Practise 300-410 questions linked to Route Redistribution.
Policy-Based Routing (PBR) practice questions
Practise 300-410 questions linked to Policy-Based Routing (PBR).
VRF-Lite practice questions
Practise 300-410 questions linked to VRF-Lite.
Route Maps and Route Filtering practice questions
Practise 300-410 questions linked to Route Maps and Route Filtering.
Administrative Distance practice questions
Practise 300-410 questions linked to Administrative Distance.
Route Summarization practice questions
Practise 300-410 questions linked to Route Summarization.
Bidirectional Forwarding Detection (BFD) practice questions
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
VPN Technologies practice questions
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Start a free 300-410 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 300-410 question test?
SNMP Troubleshooting — This question tests SNMP Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: An ACL is applied to the SNMP community string that does not permit the NMS IP address. — The debug output on R2 shows packets from the NMS (10.1.1.100) to R2's Loopback0 (10.2.2.2) being dropped with 'access-list violation'. Since no ACL is applied to any interface on R2, the only remaining ACL that could cause this is an SNMP community ACL. The SNMP community string 'public' or 'private' can have an optional ACL applied via the 'snmp-server community <string> [view <view-name>] [ro|rw] [acl-number]' command. If that ACL does not permit the NMS IP address (10.1.1.100), the router will silently drop SNMP packets from that source, even though no interface ACL exists. This matches the symptom exactly.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More 300-410 practice questions
- Drag and drop the steps to negotiate an IKEv2 IPsec site-to-site tunnel into the correct order, from first to last.
- Drag and drop the steps to troubleshoot an IPsec site-to-site VPN adjacency failure into the correct order, from first t…
- Drag and drop the steps to verify and validate the operational state of an IPsec site-to-site VPN into the correct order…
- Consider the following configuration snippet: ip cef ! interface GigabitEthernet0/0 ip address 10.0.0.1 255.255.255.25…
- A router is configured with 'logging host 10.1.1.100' and 'logging trap informational'. The engineer notices that syslog…
- Drag and drop the steps to configure a GRE tunnel for IPv6 over IPv4 into the correct order, from first to last.
Last reviewed: Jul 4, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.