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AdvancedPublished 2026-06-09

CCNP: OSPF Backbone & Area Mismatch Recovery

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Advanced multi-area OSPF lab with a realistic two-site design and a WAN ABR. You will deploy OSPF with a backbone (area 0) and a non-backbone area, intentionally create an area mismatch on one transit link to observe the failure, then correct it to restore full reachability. The final build demonstrates solid OSPF hygiene and SSH-only management.

Track
Est. time
85 minutes
Difficulty
Advanced
Topics

Learning objectives

  • Deploy OSPF across a backbone and a non-backbone area with an ABR connecting them
  • Pin router-ids, use passive-interface default, and match network statements to real links
  • Interpret OSPF neighbor states and LSDB to verify and troubleshoot adjacency issues
  • Diagnose and fix an OSPF area mismatch on a transit link
  • Restore end-to-end traffic and confirm proper route visibility from hosts and routers

Troubleshooting focus

  • No OSPF adjacency forms on a transit: Confirm both ends are in the same area. show ip ospf interface gives the area per interface, show ip ospf neighbor sits in DOWN/INIT, and the logs cite a mismatched area ID.; Confirm the transit is un-passive on both ends. A passive transit sends no hellos, so no neighbor forms even with correct areas.; Verify the IP address and mask on both ends of the transit and that the link is up/up.
  • An interface you expected in OSPF never appears in show ip ospf interface: the network statement's wildcard is too broad or too narrow. It must match the real subnet exactly.
  • HOST-A-CLIENT cannot ping 10.20.1.10: traceroute from the host to find the first router with no route to the far LAN, then inspect that router's OSPF database and interfaces.

Topology

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Grade your work

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.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
  • You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
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