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IntermediatePublished 2026-07-11

CCNA OSPF Day 7: Passive Interfaces + Default Origination

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Deploy OSPFv2 across a small branch-to-edge topology, mark user-LAN interfaces passive, and originate a default route at the edge so branch hosts learn O*E2 and can reach an internet-facing host. You will implement, verify, and troubleshoot OSPF passive interfaces and default-information originate.

Track
Est. time
55 minutes
Difficulty
Intermediate
Topics

Learning objectives

  • Configure OSPFv2 with explicit router-ids and correct network statements on all routers
  • Apply passive-interface default and selectively unpassive only transit interfaces
  • Originate a default route into OSPF (E2) from the edge router using default-information originate
  • Verify end-to-end connectivity from the branch host to an internet-facing host and interpret OSPF route types
  • Use show/troubleshooting commands to confirm neighbors, LSAs, and routing tables

Troubleshooting focus

  • If neighbors are not FULL: Confirm both ends of a transit link are in area 0 and unpassive (show ip ospf interface brief); Check IP addressing/masks on transit interfaces and that they are no shutdown
  • If the branch lacks O*E2: Verify RTR-EDGE has a static default (show ip route 0.0.0.0) and default-information originate under OSPF
  • If the branch can’t reach 203.0.113.10 specifically: Ensure RTR-EDGE advertises 203.0.113.0/24 into OSPF; on RTR-BRANCH you should see an O route for that prefix
  • If host pings fail but routing looks correct: Verify host IP/gateway on each Alpine node; confirm ARP on the router’s LAN interface (show ip arp) and interface status (show ip interface brief)

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.
  • Scored something you believe is correct? Use Report an issue on this page — that is exactly how the grading fixes in the changelog got found.

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