The answer is that the exporter source interface does not match what the collector expects. NetFlow exports rely on the source interface having a valid Layer 3 path to the collector; if the exporter sends records out the wrong interface, the collector either drops them due to an unexpected source IP or never receives them at all. On the CCNA 200-301 v2 exam, this scenario tests your understanding that the `ip flow-export source` command must reference an interface whose IP address the collector is configured to accept—a common trap is assuming the collector IP is the problem when it is actually the source selection. Remember the memory tip: “Source must match the collector’s expectation, not just any path to the destination.”
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: netFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port.. 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.
Exhibit
ip flow-export destination 10.99.99.50 2055
ip flow-export source Loopback0
interface Loopback0
ip address 172.16.255.1 255.255.255.255
interface GigabitEthernet0/0
ip address 10.99.99.2 255.255.255.0
Collector subnet: 10.99.99.0/24
Collector accepts exports only from 10.99.99.2
A collector is not receiving flow records from a branch router. Based on the exhibit, 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.
ip flow-export destination 10.99.99.50 2055
ip flow-export source Loopback0
interface Loopback0
ip address 172.16.255.1 255.255.255.255
interface GigabitEthernet0/0
ip address 10.99.99.2 255.255.255.0
Collector subnet: 10.99.99.0/24
Collector accepts exports only from 10.99.99.2
A
The export destination port 2055 is invalid for flow export.
Why wrong: 2055 is commonly used for NetFlow collectors.
B
The exporter source interface does not match what the collector expects.
Exports are sourced from Loopback0 instead of the accepted 10.99.99.2 address.
C
NetFlow can run only on serial interfaces.
Why wrong: NetFlow is widely used on Ethernet interfaces.
D
The router must use TCP instead of UDP to export flows.
Why wrong: NetFlow exports are commonly sent over UDP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The exporter source interface does not match what the collector expects.
The exporter is configured to send records out the wrong interface. NetFlow exports must use a source interface that has a valid path to the collector and typically matches the interface the collector expects. The collector IP itself is correct in the example, but the source interface selection is wrong.
Key principle: NetFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port.
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 export destination port 2055 is invalid for flow export.
Why it's wrong here
2055 is commonly used for NetFlow collectors.
When this WOULD be correct
In a different scenario where a question specifies that the collector is configured to listen on a non-standard port (e.g., 2056) for flow exports, option A would be correct. The question would need to indicate that the collector's configuration does not match the export destination port set on the router.
✓
The exporter source interface does not match what the collector expects.
Why this is correct
Exports are sourced from Loopback0 instead of the accepted 10.99.99.2 address.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
NetFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port.
✗
NetFlow can run only on serial interfaces.
Why it's wrong here
NetFlow is widely used on Ethernet interfaces.
When this WOULD be correct
In a different scenario where the question specifies that NetFlow is only configured on serial interfaces and the collector is set to receive flows exclusively from those interfaces, this option could be correct. For example, if the question states that the branch router is only exporting flows from a serial interface, then this option would apply.
✗
The router must use TCP instead of UDP to export flows.
In a different question scenario where the exam specifies that the network configuration mandates the use of TCP for flow export due to reliability concerns, this option would be correct. For instance, if the question indicated that the collector requires TCP for secure transmission of flow records, then this would be the right answer.
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 exporter source interface does not match what the collector expects.Correct answer▾
Why this is correct
Exports are sourced from Loopback0 instead of the accepted 10.99.99.2 address.
✗The export destination port 2055 is invalid for flow export.Wrong answer — click to see why▾
Why this is wrong here
Port 2055 is a well-known default port for NetFlow collectors and is widely supported. The issue is not with the port number.
★ When this WOULD be the correct answer
In a different scenario where a question specifies that the collector is configured to listen on a non-standard port (e.g., 2056) for flow exports, option A would be correct. The question would need to indicate that the collector's configuration does not match the export destination port set on the router.
Why candidates choose this
Students may confuse 2055 with other common ports or think that non-standard ports are invalid, but 2055 is standard for NetFlow.
✗NetFlow can run only on serial interfaces.Wrong answer — click to see why▾
Why this is wrong here
NetFlow can be configured on various interface types including Ethernet, serial, and others. It is not limited to serial interfaces.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that NetFlow is only configured on serial interfaces and the collector is set to receive flows exclusively from those interfaces, this option could be correct. For example, if the question states that the branch router is only exporting flows from a serial interface, then this option would apply.
Why candidates choose this
Older NetFlow implementations or legacy exam questions sometimes focus on serial interfaces, leading to the misconception that NetFlow only works on serial links.
✗The router must use TCP instead of UDP to export flows.Wrong answer — click to see why▾
Why this is wrong here
NetFlow exports use UDP as the transport protocol because it is lightweight and suitable for streaming flow data. TCP is not used due to overhead and connection management.
★ When this WOULD be the correct answer
In a different question scenario where the exam specifies that the network configuration mandates the use of TCP for flow export due to reliability concerns, this option would be correct. For instance, if the question indicated that the collector requires TCP for secure transmission of flow records, then this would be the right answer.
Why candidates choose this
Students may think TCP is more reliable and thus better for data export, but NetFlow is designed for UDP to minimize impact on router performance.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common exam trap is to focus on the export destination port or protocol when flow records are not received. Since UDP port 2055 is the default and valid port for NetFlow exports, candidates might incorrectly assume the port is wrong. Another trap is thinking NetFlow only works on serial interfaces, leading to confusion when Ethernet interfaces are used. The real issue often lies in the source interface configuration, where the router exports flow records from an interface IP address that the collector does not expect or trust, causing the collector to drop the data silently.
Detailed technical explanation
How to think about this question
NetFlow is a Cisco technology used to collect IP traffic information and monitor network flow data. It exports flow records from routers or switches to a collector device, which analyzes traffic patterns for security, performance, or troubleshooting purposes. The export process relies on UDP packets sent from a specific source interface on the router to the collector's IP address and port. The source interface selection is critical because it determines the source IP address used in the export packets, which must be reachable and recognized by the collector.
When configuring NetFlow export, the router must use a source interface that has a valid routing path to the collector and matches the IP address expected by the collector for incoming flow records. If the source interface is incorrectly set, the collector may reject or drop the flow records because the source IP address does not match the configured or trusted address. This mismatch causes the collector to not receive or process the flow data, even if the destination IP and port are correct.
A common exam trap involves assuming that the export destination port or protocol is the issue, but NetFlow typically uses UDP port 2055 by default, which is valid. Another confusion is thinking NetFlow only runs on certain interfaces like serial, but it works on Ethernet interfaces as well. The practical behavior is that the source interface must be explicitly configured to an interface with a stable and routable IP address, often a loopback interface, to ensure consistent flow export and collector acceptance.
KKey Concepts to Remember
NetFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port.
The source interface for NetFlow export determines the source IP address seen by the collector and must be reachable and trusted.
Collectors reject flow records if the source IP address does not match the expected or configured address, causing data loss.
NetFlow commonly uses UDP port 2055 for exporting flow data, which is a valid and standard destination port.
NetFlow can run on Ethernet interfaces as well as serial interfaces, so interface type does not restrict flow export.
Configuring the source interface to a loopback interface is a best practice to ensure stable and consistent flow export IP addressing.
The export destination IP must be correct, but the source interface mismatch is a frequent cause of flow record delivery failure.
UDP is the transport protocol used for NetFlow exports; TCP is not used for this purpose.
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
NetFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port.
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 200-301 question in full detail.
Review netFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — NetFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port..
What is the correct answer to this question?
The correct answer is: The exporter source interface does not match what the collector expects. — The exporter is configured to send records out the wrong interface. NetFlow exports must use a source interface that has a valid path to the collector and typically matches the interface the collector expects. The collector IP itself is correct in the example, but the source interface selection is wrong.
What should I do if I get this 200-301 question wrong?
Review netFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port., then practise related 200-301 questions on the same topic to reinforce the concept.
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?
NetFlow exports flow records using UDP packets from a router's source interface to a collector's IP address and port.
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