Define the problem
Check whether one computer, several computers, Wi-Fi only, or the entire network is affected.
Overview
Use this structured process when a laboratory computer cannot connect to the local network or the internet.
Step-by-step procedure
Check power and cables
Confirm that the router and switch are powered, Ethernet plugs are secure, and link lights are active.
Check the network adapter
Make sure wired or wireless networking is enabled and airplane mode is off.
Inspect IP settings
Confirm the computer has a valid address, subnet mask, gateway, and DNS. An address beginning with 169.254 usually means DHCP failed.
Test the gateway
Ping the router. If it fails, focus on the cable, adapter, switch port, Wi-Fi signal, or local IP configuration.
Test external connectivity
Ping a public IP address. If the gateway works but the public IP fails, check the router WAN connection or provider service.
Test DNS
Open a website or resolve a domain name. If public IP tests work but names fail, verify DNS settings.
Apply one fix at a time
Reconnect the cable, try a known-good cable or port, renew DHCP, restart the adapter, then restart authorized network devices only if needed.
Document the result
Record the cause, fix, affected device, cable or port number, and date for future maintenance.
Checks and reminders
- Never change several settings at once because this hides the actual cause.
- Do not factory-reset routers or switches without authorization and a backup.
- Escalate damaged ports, burning smells, overheating, or repeated outages immediately.