Reviewed by Router Setup Editorial Team Last reviewed:

A wired link can be limited by negotiated port speed, cable quality, an older switch, powerline equipment, adapter drivers or the upstream Internet service.

First checks

  1. Check the negotiated Ethernet speed on the client and router or switch port.
  2. Replace the cable with a known-good cable rated for the intended link.
  3. Connect directly to the primary router to bypass switches, docks and powerline adapters.

How to interpret the result

A 100 Mb/s negotiation usually points to a cable, connector or port limitation even when traffic still passes. If the link negotiates at 1 or 2.5 Gb/s but Internet remains slow, compare local file transfer or another wired client to separate LAN capability from the ISP path.

What this symptom usually does not prove

Do not change Wi‑Fi channels or wireless security to troubleshoot a wired link.

Escalate with useful evidence

Record which devices are affected, whether Ethernet and Wi‑Fi behave differently, the router or gateway status, and the exact time of the fault. This evidence helps distinguish a local client issue, radio problem, routing policy, upstream service fault or failing hardware.

Before a factory reset

Restart the relevant device first and save any ISP, Wi‑Fi, reservation, port-forwarding or mesh information needed to rebuild the network. A factory reset is a configuration-recovery action, not a universal diagnostic test.

Related troubleshooting

Safety: Do not share router passwords or remote-control codes to diagnose this symptom.