Troubleshoot an Ethernet device on Mac
If you have an Ethernet device (such as a DSL or cable modem, or an Ethernet hub or router) connected to your Mac, and it doesn’t seem to be working properly, check the cables and network settings, and restart the device and your Mac.
Check the Ethernet cable to make sure it’s not damaged.
Make sure the Ethernet cable is securely connected to the Ethernet port on your computer and the device. Remove the cable, then reconnect it to make sure it’s connected properly.
Make sure your network settings are correct. If you’re not sure which settings to use, contact your ISP.
Shut down your Mac, then turn off the Ethernet device. Wait a few minutes, then turn the Ethernet device back on. Wait until it has started up completely, then restart your Mac.