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300-410 Practice Question: Runs the following command to troubleshoot a…

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# debug ip ospf adj

OSPF adjacency debugging is on R1#

*Mar  1 00:05:23.123: OSPF: Rcv pkt from 10.1.1.2, FastEthernet0/0, area 0.0.0.0, packet type: 1 (Hello)
*Mar  1 00:05:23.123: OSPF: 2 Way Communication to 10.1.1.2 on FastEthernet0/0, state 2WAY
*Mar  1 00:05:23.124: OSPF: Send immediate hello to nbr 10.1.1.2, src address 10.1.1.1, on FastEthernet0/0
*Mar  1 00:05:23.124: OSPF: Rcv pkt from 10.1.1.2, FastEthernet0/0, area 0.0.0.0, packet type: 2 (DBD)
*Mar  1 00:05:23.125: OSPF: Rcv DBD from 10.1.1.2, seq 0x1234, opts 0x2, flag 0x7, mtu 1500 state EXSTART
*Mar  1 00:05:23.126: OSPF: Nbr 10.1.1.2 has state FULL

What does this output indicate?

⚠ Common exam trap

Cisco often tests the misconception that any debug output showing OSPF packet reception implies a problem, when in fact the sequence of states (2WAY to FULL) indicates successful adjacency formation, and candidates may incorrectly attribute normal behavior to CoPP failure.

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

OSPF adjacency is established successfully, indicating CoPP is not blocking OSPF traffic.

The debug output shows the OSPF adjacency progressing through the expected states (2WAY, EXSTART) and reaching FULL after receiving a Database Description (DBD) packet. This confirms that OSPF Hello and DBD packets are being processed normally, which means Control Plane Policing (CoPP) is not dropping OSPF traffic. CoPP would typically drop packets at the control plane, preventing state transitions like 2WAY or FULL.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • OSPF adjacency is failing due to CoPP dropping Hello packets.

    Why it's wrong here

    The output shows successful Hello exchange and transition to FULL state.

  • OSPF adjacency is established successfully, indicating CoPP is not blocking OSPF traffic.

    Why this is correct

    The adjacency reached FULL state, meaning OSPF packets are being processed correctly.

  • OSPF is experiencing packet loss due to MTU mismatch.

    Why it's wrong here

    The MTU of 1500 is mentioned, but no errors are indicated.

  • OSPF is stuck in EXSTART state due to CoPP.

    Why it's wrong here

    The output shows transition from EXSTART to FULL.

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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