Fiber ONT LEDs identify optical and Ethernet stages, but their colors vary by ONT model. A healthy optical light does not prove the router WAN is configured.
Before you change anything
This is a diagnostic entry point. The source supports the general check, not a confirmed root cause for your device.
What to check first
Does the same failure occur on a wired client connected to the router?
Record the exact model, hardware revision, firmware and recent change before adjusting settings. If you cannot answer the question, keep the cause open.
Narrow the likely path
| Observation | Next check |
|---|---|
| WAN link is down | Inspect the modem/ONT, Ethernet cable, intended WAN port and provider status. |
| WAN address is absent | Check the ISP connection type and upstream gateway without changing Wi-Fi settings. |
| WAN address exists | Separate DNS-only failures from total upstream failures. |
Decision after the first test
Use the ONT's own chart, then check its Ethernet handoff and the router WAN address. Ask the ISP about authentication if the link is present but no address arrives.
Use a documented next step
Verify before escalating
After each change, repeat the exact failed task. If the result is unchanged, restore the previous setting and use the official support link for your exact hardware revision. Don’t assume a menu or capability from a related model.
Official sources
- TP-Link no-internet: WAN address and cabling checks (full_text; checked 2026-11-01)
Check your exact US model, hardware revision, and firmware on the linked support page before changing settings.