How physical links, DHCP, gateways, DNS, and Wi-Fi conditions produce different connectivity symptoms.
Network diagnosis becomes faster when link state, addressing, routing, name resolution, and Wi-Fi conditions are tested in that order.
| Symptom | First path |
|---|---|
| No link light or failed Wi-Fi association | Cable, NIC, access point, SSID, credentials, signal, or radio state |
169.254.x.x address |
DHCP or local addressing |
| Valid address but no gateway or external-IP access | Gateway, router, or upstream connection |
| External IP works but hostnames fail | DNS |
| Only one room or wireless client fails | Placement, interference, band, or client-specific configuration |
Test one layer at a time. Good Wi-Fi signal does not prove that a client received an address or can reach the gateway; a successful IP connection does not prove DNS is working.