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300-410 Practice Question: A large enterprise network is experiencing…

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.

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.

  • 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.

Visual reference

R1 R2 R3 R4 10 100 10 100 OSPF picks R1→R2→R4 (cost 20) over R1→R3→R4 (cost 200)

Quick reference

Routing Protocol Comparison

ProtocolMetricMax HopsAlgorithmType
RIP v2Hop count15Bellman-FordDistance vector
OSPFCost (bandwidth)UnlimitedDijkstra (SPF)Link state
EIGRPComposite metricUnlimitedDUALHybrid
IS-ISCostUnlimitedDijkstraLink state
BGPPolicy / attributesUnlimitedPath vectorPath vector

RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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