Troubleshooting labs
The real CCNA® exam puts you on a broken network and asks you to fix it. Each lab below does exactly that — a partially-configured device with one realistic fault. Diagnose it with show commands, fix it by typing real Cisco IOS, and the objectives tick off live when you get it right.
OSPF neighbor never comes up
R1 and R2 should be OSPF neighbors on the link between them, but on R2 the neighbor table is empty and the two LANs can’t reach each other. Diagnose R2 with the show commands and bring the adjacency to FULL — there’s more than one valid fix.
Open the lab →A blocked host still reaches the server
An ACL is supposed to stop one host from reaching a server, but the host still connects. Find why it isn’t taking effect and make it block the right traffic — two valid fixes exist.
Open the lab →The LAN can’t reach the internet
PAT is configured but inside hosts still can’t reach the internet and nothing is being translated. Investigate the NAT setup, find what’s incomplete, and get translations forming.
Open the lab →A VLAN won’t cross the trunk
VLAN 20 hosts can’t reach the other switch even though VLAN 10 works across the same trunk. Find why VLAN 20 isn’t crossing and restore connectivity.
Open the lab →Want every fault to feel obvious?
1:1 mentorship walks you through troubleshooting on a real network, with live feedback. First session free.