Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
ip flow-export destination 192.0.2.50 2055 ip flow-export source Loopback0 ! interface Loopback0 ip address 10.255.255.1 255.255.255.255 Collector routing table has no route to 10.255.255.1.
A router is configured for NetFlow export, but the collector at 192.0.2.50 is not receiving any flow records. Based on the exhibit, what is the most likely problem?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
The exporter must use TCP instead of UDP.
Traditional NetFlow export commonly uses UDP, so that is not the issue.
B
Best answer
The collector cannot return traffic to the configured export source address.
The source address must be reachable.
C
Distractor review
NetFlow can be enabled only on serial interfaces.
It can be used on many interface types.
D
Distractor review
The destination port must be 514.
UDP 514 is associated with Syslog, not NetFlow export.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is to assume that NetFlow export must use TCP or a specific port like UDP 514, which is actually reserved for Syslog. Candidates might also mistakenly believe NetFlow can only be enabled on serial interfaces, which is incorrect. The real issue often lies in the source IP address configured for export: if the collector cannot route back to this source, no flow records will be received. This reachability problem is subtle because the export destination and port may be correct, misleading candidates to focus on transport protocol or port numbers instead of routing and source interface configuration.
Technical deep dive
How to think about this question
NetFlow is a Cisco technology that collects IP traffic information as it enters or exits an interface. The router acting as the NetFlow exporter sends flow records to a collector, which analyzes traffic patterns. The export process relies on UDP packets sent from a source IP address configured on the router, often tied to a specific interface such as a loopback for stability. The collector must be able to route return traffic to this source IP to maintain proper flow communication. When configuring NetFlow export, the source interface selection is critical because it defines the source IP address used in the UDP packets. If the collector cannot route back to this source IP, flow records will not be received. This reachability requirement means that the source IP must be part of a routable network segment accessible from the collector's location. The export destination IP and UDP port must also be correct, but these are less commonly the cause of failures compared to source IP reachability. A common exam trap is assuming that NetFlow export requires TCP or a specific port like 514, which is actually used for Syslog. Another trap is thinking NetFlow only works on serial interfaces, whereas it supports multiple interface types. The practical implication is that network engineers must verify routing paths and source interface reachability when troubleshooting NetFlow export issues, especially when using loopback interfaces as the export source.
KKey Concepts to Remember
- NetFlow export requires the source IP address used by the exporter to be reachable and routable from the collector to ensure bidirectional communication.
- The NetFlow exporter typically sends flow records using UDP, and the collector listens on a specific UDP port, commonly 2055, not TCP or port 514.
- Configuring the export source interface on a router determines the source IP address for NetFlow packets, which must be accessible by the collector for successful flow reception.
- NetFlow can be enabled on various interface types, including Ethernet and serial interfaces, so interface type restrictions do not prevent flow export.
- The collector must be able to send return traffic to the exporter's source IP address to acknowledge or manage flow data, making routing and reachability critical.
- UDP port 514 is used for Syslog messages, not for NetFlow export, which uses different UDP ports such as 2055, 9995, or 9996 depending on configuration.
- Selecting a loopback interface as the export source is common for stability, but it requires proper routing so the collector can reach that loopback address.
- NetFlow export failures often result from misconfigured source addresses or unreachable source IPs rather than transport protocol or port mismatches.
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
NetFlow export requires the source IP address used by the exporter to be reachable and routable from the collector to ensure bidirectional communication.
What is the correct answer to this question?
The correct answer is: The collector cannot return traffic to the configured export source address. — The exporter is sourcing packets from Loopback0, but the collector cannot route back to 10.255.255.1. NetFlow export often works only when the source interface address is reachable from the collector side. The export destination and port are configured, but the chosen source creates the actual reachability issue.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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