What this page covers
Check negotiated link speed first; an Internet speed test alone cannot identify the physical bottleneck.
Step-by-step workflow
- Read the negotiated link speed on the client or switch.
- Swap one cable and one known-good port.
- Compare the same device at another authorised port.
- Keep auto-negotiation unless the manufacturer documents another requirement.
Decision table
| Check | What it tells you | Safe next action |
|---|---|---|
| Link is 100 Mbps | Physical path or port may limit the link | Swap cable/port systematically |
| Link is 1 Gbps, Internet slow | WAN or service path is separate | Test gateway and ISP path |
| Only one wall jack fails | In-wall termination may be involved | Use a direct cable comparison |
Limits and verification
Do not force duplex or speed without documentation; mismatched settings can make the link less stable.
Official sources
- Microsoft — Essential network settings and tasks (Windows network fields and commands)
- CISA — Securing Home Network Devices (home-network safety guidance)
Related Router Portal guides
Router login troubleshooting · Subnet calculator
Keep in mind: Firmware, operating-system menus, ISP policies and regional radio rules can change. Confirm the current official source and exact device before applying a setting.
Our networking steps are lab-tested against standard RFC 1918 private networking protocols across Windows 11 (24H2), macOS Sequoia (15.1), iOS 18, and Android 15. We verify physical device labels and firmware release documentation before publishing gateway instructions. Router Portal is strictly read-only and never requests, intercepts, or logs router passwords.