- A
The flow exporter is misconfigured with the wrong export protocol; it should be netflow-v5.
Why wrong: NetFlow v9 is valid and commonly used; v5 is older and less capable.
- B
The collector IP is not reachable due to a missing route; the summary route for Loopback0's subnet does not include the /32 host route.
If Loopback0's /32 is not in the routing table of the collector's router, packets from that source may be dropped. The summary route may not cover the exact host address.
- C
The UDP port 2055 is blocked by an ACL on R1's outbound interface.
Why wrong: The show output shows 0 packets exported, not dropped packets; ACL blocking would typically show errors or drops.
- D
The flow monitor is not applied to any interface, so no flows are being exported.
Why wrong: The question states NetFlow data loss, but the exporter statistics show 0 packets exported; this could be due to no flows, but the scenario implies flows exist but are not exported.
300-410 NetFlow and Flexible NetFlow Practice Question
This 300-410 practice question tests your understanding of netflow and flexible netflow. 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 loss of NetFlow data from multiple routers. Router R1 has the following relevant configuration: flow exporter EXPORTER-1 destination 10.1.1.1 source Loopback0 transport udp 2055 export-protocol netflow-v9. Router R2 shows: R2# show flow exporter EXPORTER-1 statistics | include (Packets|Errors) Packets exported: 0, Errors: 0. The network uses OSPF, and R1's Loopback0 is reachable via a summary route. What is the root cause?
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 collector IP is not reachable due to a missing route; the summary route for Loopback0's subnet does not include the /32 host route.
The issue is that the NetFlow exporter's source interface (Loopback0) is not the same as the interface used to reach the collector (10.1.1.1). OSPF summarization may cause the source IP to be unreachable from the collector's perspective due to routing asymmetry or the summary route not including the specific /32. The correct fix is to ensure the source interface is the one with a route to the collector, or to use a loopback that is explicitly advertised.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 flow exporter is misconfigured with the wrong export protocol; it should be netflow-v5.
Why it's wrong here
NetFlow v9 is valid and commonly used; v5 is older and less capable.
- ✓
The collector IP is not reachable due to a missing route; the summary route for Loopback0's subnet does not include the /32 host route.
Why this is correct
If Loopback0's /32 is not in the routing table of the collector's router, packets from that source may be dropped. The summary route may not cover the exact host address.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The UDP port 2055 is blocked by an ACL on R1's outbound interface.
Why it's wrong here
The show output shows 0 packets exported, not dropped packets; ACL blocking would typically show errors or drops.
- ✗
The flow monitor is not applied to any interface, so no flows are being exported.
Why it's wrong here
The question states NetFlow data loss, but the exporter statistics show 0 packets exported; this could be due to no flows, but the scenario implies flows exist but are not exported.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
The show output shows 0 packets exported, not dropped packets; ACL blocking would typically show errors or drops.
Scenario analysis trap
The question states NetFlow data loss, but the exporter statistics show 0 packets exported; this could be due to no flows, but the scenario implies flows exist but are not exported.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 300-410 question test?
NetFlow and Flexible NetFlow — This question tests NetFlow and Flexible NetFlow — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The collector IP is not reachable due to a missing route; the summary route for Loopback0's subnet does not include the /32 host route. — The issue is that the NetFlow exporter's source interface (Loopback0) is not the same as the interface used to reach the collector (10.1.1.1). OSPF summarization may cause the source IP to be unreachable from the collector's perspective due to routing asymmetry or the summary route not including the specific /32. The correct fix is to ensure the source interface is the one with a route to the collector, or to use a loopback that is explicitly advertised.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 19, 2026
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