Troubleshoot Hardware Problems with Your MacBook Network
Although many things on a network can go bad or cause problems, usually network problems are caused by faulty equipment or wiring. Sometimes it’s something as simple as a cable not being plugged in snugly. Looking at the physical cables, connections, and equipment is always the best place to start looking for problems.
Here is a quick list of physical things to check while trying to fix network problems:
Make sure that both ends of the network cable are firmly connected.
First check the end that plugs into the computer and then check the end that connects to the switch.
Turn on the problematic computer to be sure that it’s connected to a hub or switch.
Check the port on the switch to see whether the link/speed light is lit. (Depending on the switch that you have, you might not have a link light. Many switches use a speed light to indicate a link. Check the manufacturer’s manual for your model.) If your computer is on and connected but no link/speed light is lit, try replacing the network cable.
If you replace the network cable and there still isn’t light, try unplugging the cable from the switch and plug it into another port.
Choose one of the other computers connected to the switch that works, unplug it, and plug the broken computer into that port for testing. Occasionally, a single port on a switch goes bad; if that happens, just mark it as bad and don’t use it anymore.
But if all computers connected to the switch stop working, it’s probably the switch that’s gone south. If the switch is still under warranty, get it fixed or replaced. (If the warranty has expired, it’s usually cheaper to replace a switch than fix it.)
If you replace the cable, try a different port on the switch, and if other computers work fine on that switch, the NIC inside your computer has possibly gone bad.
If you reach this determination, call your local service center to have it looked at and repaired. If you have an older model on which the NIC was added instead of built in, you can simply replace the NIC yourself — MacBook owners, unfortunately, don’t have this option.
The key when troubleshooting physical problems is the link/speed light on the switch. If the link/speed light still doesn’t work, the problem likely isn’t physical. Start troubleshooting the network configuration on the computer itself.