Pattern to record: Link changes when the cable is reseated or one speed never negotiates.

Separate the adapter from the network

For motherboard Ethernet, separate the physical link from Windows configuration. Record the board model, link speed and switch-port behaviour; successful Wi-Fi access does not test the wired controller. One possible explanation is that one spring contact no longer aligns with the cable plug.

Link and configuration checks

1. Test a known switch and cable, inspect port magnetics and compare pre-boot and Windows detection.
2. Inspect all eight contacts and compare a known undamaged cable.

Before internal work

Lightning or surge damage can extend beyond the visible network port. Probing a powered port with metal can short magnetics or power.

Verify the network path

If the checks support this cause, replace the connector or complete interface assembly. Verification should cover cold start, negotiated speed, sustained transfer, restart and wake-on-LAN if used.

For an assessment of your desktop computer, contact AEPC in Burswood or call 027 908 8880. Provide the model and the conditions that reproduce this problem. Workshop visits are by appointment.