A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.
It's the Monday after a long weekend. Your monitoring shows a cascade of alerts: VLAN 30 users can't reach the file server, branch office OSPF neighbor is flapping, one access switch is at 95% CPU, and NAT translation counts are unusually low. Are these related? Or four separate problems? You have one hour before the executive team notices. Where do you start?
Multi-fault scenarios are realistic and stressful. Real networks don't break one thing at a time. This lab simulates a network with three or four injected faults and challenges you to find them all — methodically, efficiently, without breaking anything else.
Use any topology from the previous labs (three routers, two switches, several hosts). Ask an instructor or another learner to inject 3–4 faults, OR inject them yourself for self-testing. Common fault types to inject:
Inject 3–4 faults. Then troubleshoot systematically without looking at your injected-fault notes. Time yourself. The goal is to identify all faults within 45 minutes. Afterward, review each fault: what was the diagnostic evidence? Which tool or command revealed it? Could you have found it faster?
You've found a trunk with a native VLAN mismatch and a router with a wrong static route. Users are complaining that the file server is unreachable. Which fault do you fix first?
Select the safest next action.
Section 20 complete. Ten labs cover the full CCNA blueprint hands-on: basic config, VLANs, routing, STP, EtherChannel, static routing, OSPF, services, security, wireless, and multi-fault troubleshooting. Section 21 is exam preparation — the last section of the course.
Finish the lesson once you have worked through the material. This awards ★ 30 XP.