Define the scope first
Determine whether one client, every client on an AP, or the whole wired and wireless network is affected. Record the start time and last change, then compare with a working client.
| Stage | Check | If it fails |
|---|---|---|
| 1 Power | LEDs, adapter, UPS, heat | Check the power path and ratings |
| 2 Link | Port LED, cable, negotiated rate | Cross-test a known-good cable and port |
| 3 Address | IP, mask, gateway, DHCP lease | 169.254.x.x points to the DHCP path |
| 4 Local | Ping gateway, open management UI | Check VLAN, Wi-Fi association and host firewall |
| 5 DNS | Test an external IP and a name | If only IP works, inspect DNS |
| 6 WAN | Router WAN IP and carrier state | Check ONT/modem and ISP status |
Fast symptom branches
- Wi-Fi connects but is slow: compare RSSI, congestion, band and wired backhaul.
- Only the NAS is missing: test reservation, VLAN firewall and direct IP instead of DNS name.
- Only some sites fail: separate DNS, MTU, IPv6 path and browser issues.
- Intermittent drops: correlate logs, temperature, DHCP renewals and cable error counters.
Change one variable at a time Retest the same way after each change. Resetting several devices together destroys evidence and extends recovery.
Incident record
Record time / affected clients / wired or wireless / IP / gateway / DNS / WAN / last change / test result to compare recurring faults.