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AdvancedPublished 2026-07-12

CCNA Foundations: OSPF Day 8 — OSPF Troubleshooting Capstone

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Advanced CCNA OSPF troubleshooting capstone on Cisco Modeling Labs (CML-Free). A three-router, two-host enterprise-style topology is pre-broken with multiple independent OSPF faults. Your job: diagnose and fix them so adjacencies form across areas and the end hosts can reach each other. The final solution forwards end-to-end and adheres to clean OSPF hygiene.

Track
Est. time
65 minutes
Difficulty
Advanced
Topics

Learning objectives

  • Diagnose and repair OSPF adjacency failures due to area mismatches and interface timer mismatches
  • Identify and correct incorrect OSPF network statements and wildcard masks
  • Implement OSPF hygiene: explicit router-ids, passive-interface default with selective exceptions, and advertising loopbacks
  • Verify OSPF neighbor states, LSDB synchronization, and end-to-end reachability from hosts

Troubleshooting focus

  • No neighbor on the RTR-SITEA-EDGE–RTR-HUB link: compare the network statement wildcard for 10.0.12.0/30; confirm the interface is up/up and not passive.
  • No neighbor on the RTR-HUB–RTR-SITEC-EDGE link: confirm both ends share an area and hello/dead timers in show ip ospf interface Ethernet0/0. If timers match, compare MTU.
  • A neighbor stuck in EXSTART/EXCHANGE: look for an MTU mismatch or duplicate router-ids.
  • CLIENT-A reaches 10.10.1.1 but not 10.10.3.10: check show ip route ospf for inter-area routes on the ABR, and that LAN interfaces are passive.
  • An interface missing from OSPF or in the wrong area: show ip ospf interface brief lists each interface and its area.

Topology

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How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
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