We are using an IPcop firewall with the local LAN port feeding a Netgear EN108 hub with 4 devices connected. The "link" light on all the other ports shows steady on, as it should. For a long time the link light from the Macbook port also works properly as it should, but now the link does not show steady any longer, but just flashes, along with the RXData light on the hub as well, when trying to connect. The Macbook then goes to a 169.254.x.x self-assigned address (useless). Have done a power reset on the hub, and rebooted the router here, no difference. The apparent symptom is that the ethernet jack on the macbook is no longer working properly here at home. We have a wireless AP connected to another port on the hub and it also is getting an address from the firewall/router and is working properly. This is a long-term working solution that suddenly stops working with the Macbook not working with any of the hub ports - everything else still works normally. The Ethernet cable -which used to work with the Macbook - tests 100% good with a Siemon STM8 cable tester I have. Replaced the cable with another 5e ethernet cable, also tests 100% good, no difference. I took my machine in to the Apple store and it connected right away to the Store's ethernet connection. Our configuration is this: Cablemodem with static IP connects to "external" port on firewall. "Local" LAN port connects to 8-port Netgear EN108 hub which feeds several devices here, all others working normally. Swapping ports no help. Link light on hub for this one port only (Macbook port) will not come on. This has all symptoms of a Layer-1 problem but rebooting the Macbook, resetting DHCP etc does not make the link light on. What is keeping the ethernet interface on the Macbook from turning on the link light on the hub? Why does this machine not even provide a link LED? How do I test the ethernet interface at the PHY (layer 1) layer on the macbook?