A first-failing-layer connectivity diagnosis
Guided practice · Diagnose Connection Problems
Diagnose “Connected, no internet”
Use a layer-by-layer comparison to locate the first failed network boundary.
Outcome summary
Know what success looks like before you begin
Save the completed a first-failing-layer connectivity diagnosis together with the evidence recorded during each field check.
- I determined whether one or all devices are affected.
- I tested local gateway, internet IP and domain name in order.
- I repeated the original symptom after one reversible action.
Stop before factory-resetting the router or modem; record settings, provider credentials, and the state of other devices first.
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Lab brief
Know the problem and the evidence you need
A device reports that Wi-Fi or Ethernet is connected, but internet services do not work reliably.
A first-failing-layer connectivity diagnosis
Separate a one-device issue from local-link, gateway, DNS, router-WAN and provider problems without random resets.
“Connected” only confirms a local link. A layered test of device, gateway, public IP, and DNS identifies the first failing boundary without disruptive resets.
Safety and setup
Prepare before changing anything
Have this ready
- Save active work before restarting a client device or router later in the decision process.
- Do not factory-reset the router, disable firewalls or delete network configurations in this lab.
- Record the original symptom and time so the same test can be repeated.
Field checks
0 of 5 checks completeRun the lab
Complete one check at a time. Record the evidence before moving on.
Interpret results
Match the evidence to the next action
If you seeNext action
Only one device fails
Focus on that device’s adapter, saved network, proxy/VPN, driver and local security settings.
All devices fail beyond the gateway
Check router WAN status and provider service before changing every client.
Internet IP works but domains fail
Continue with the DNS resolution lab and preserve the original resolver settings.
The symptom is intermittent
Record timestamps, signal, router uptime and affected devices before escalating.
Choose the next action
Apply one reversible action at the first failed boundary; escalate router reset, firmware work or provider account changes instead of performing them as lab steps.
Confirm the evidence you produced
Finished record: A first-failing-layer connectivity diagnosis
- I determined whether one or all devices are affected.
- I tested local gateway, internet IP and domain name in order.
- I repeated the original symptom after one reversible action.