Module 4
OSPF Areas, and Two Faults That Look Alike
Why areas exist, and the two mismatches that both present as "the link is up and the neighbours will not form".
4 activities~71 min
In this module
- Explain what an area boundary stops and what it costs
- Say why every area must attach directly to area 0
- Distinguish an area mismatch from an MTU mismatch by one command
Activities
Lesson
Why OSPF has areas
The backbone rule, the border router, and the two mismatches.
11 min
Lab
OSPF multi-area
A border router with an interface in each of two areas.
20 min
Lab
Area mismatch on a new link
Two ends of one link that disagree about where they are.
20 min
Lab
OSPF stuck in ExStart
A neighbour that appears in the table and never finishes forming.
20 min
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Curriculum topics
- Routing
- Dynamic Routing
- OSPF
- Troubleshooting
Each topic page lists every lesson, quiz and hands-on lab that covers it, plus how it maps onto the CCNA and Network+ blueprints.