A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.
Third floor loses network for 3 seconds every hour. Switch log shows uplink flapping. No config changed in weeks. Cleaner bumped a fiber patch in the closet Friday. You reseat it, flap stops. Physical topology is where the bug lives.
Physical = what plugs into what. Logical = how traffic flows. Offices are wired as a star (every desk to a closet) but routed as a mesh (every subnet can reach every other). Don't mix them on the exam.
| Design | What it looks like | Used for |
|---|---|---|
| Star | Every desk to one closet switch | Every office access layer |
| Hub-and-spoke | Branches to HQ | Branch offices to HQ/data center |
| Full/partial mesh | Sites to multiple sites | WAN cores, few sites |
| Spine-leaf | Every leaf to every spine, 2 hops max | Data centers, predictable latency |
Spine-leaf wins data centers because leaf->spine->leaf is always 2 hops with all links used (ECMP). Old designs blocked extra links with spanning tree. You don't configure this for CCNA, just recognize it. Details in Modules 7-8.
100 m rule = 90 m walls + 10 m patches. If someone uses a 15 m patch cord, they've stolen from the wall budget. Flaky links love this mistake.
Fiber uplink drops 2-4 sec hourly. Logs show LINK UP/DOWN. No config change. What first?
Select the safest next action.
You can now read a floor plan. Last lesson: LAN vs WAN vs ISP, and your Module 1 capstone.
Finish the lesson once you have worked through the material. This awards ★ 45 XP.