The answer is that the source IP address 10.0.0.1 is not reachable from the collector, causing the NetFlow export source unreachable errors. This is correct because the show flow exporter output reveals ten "Source IP address unreachable" events, which specifically indicate that the router’s NetFlow exporter cannot successfully route packets from the configured source interface (10.0.0.1) to the destination collector at 192.168.1.100. While flows are still being exported, these intermittent failures point to a routing issue, such as a missing return route or an unstable interface, rather than a configuration or protocol mismatch. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret NetFlow exporter statistics and differentiate between source unreachability and other common errors like dropped packets or port misconfigurations. A common trap is assuming that successful exports mean the source is always reachable, but the counter for unreachable sources reveals transient path failures. Memory tip: "Source unreachable = routing reachability, not export failure."
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 network engineer runs the following command on Router R1:
R1# show flow exporter EXPORTER-1
Flow Exporter EXPORTER-1:
Description: Exports to collector
Export protocol: NetFlow Version 9
Transport Configuration:
Destination IP address: 192.168.1.100
Source IP address: 10.0.0.1
Transport Protocol: UDP
Destination Port: 2055
Source Port: 0
Collector Configuration:
VRFs:
Default
Options Configuration:
Sampler: Not configured
Export Statistics:
Number of Flows exported: 5000
Number of Packets exported: 250
Number of Source IP address unreachable: 10
Number of Packets dropped: 0
Based on this output, what is the most likely issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Why wrong: The counter is for source IP unreachable, not destination.
B
The source IP address 10.0.0.1 is not reachable from the destination, causing some packets to fail.
The 'Source IP address unreachable' counter indicates that the source IP is not reachable from the destination, likely due to a missing route or interface issue.
C
The UDP port 2055 is blocked.
Why wrong: If blocked, packets would be dropped, but the drop counter is 0.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The source IP address 10.0.0.1 is not reachable from the destination, causing some packets to fail.
The exporter has exported flows, but there are 10 Source IP address unreachable errors. This indicates that the source IP address (10.0.0.1) is not reachable from the destination at times, possibly due to routing issues or interface flapping.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 destination IP address is unreachable.
Why it's wrong here
The counter is for source IP unreachable, not destination.
✓
The source IP address 10.0.0.1 is not reachable from the destination, causing some packets to fail.
Why this is correct
The 'Source IP address unreachable' counter indicates that the source IP is not reachable from the destination, likely due to a missing route or interface issue.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The UDP port 2055 is blocked.
Why it's wrong here
If blocked, packets would be dropped, but the drop counter is 0.
✗
The exporter is not sending any packets.
Why it's wrong here
250 packets have been exported.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
NetFlow and Flexible NetFlow — This question tests NetFlow and Flexible NetFlow — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The source IP address 10.0.0.1 is not reachable from the destination, causing some packets to fail. — The exporter has exported flows, but there are 10 Source IP address unreachable errors. This indicates that the source IP address (10.0.0.1) is not reachable from the destination at times, possibly due to routing issues or interface flapping.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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