OS X El Capitan: Use Network Diagnostics
Use Network Diagnostics to help solve Internet connection problems. If you can’t connect to the Internet, Network Diagnostics opens and walks you through solving the problem.
Use Network Diagnostics to diagnose problems related to your Ethernet, AirPort, or internal or external modem connections. If you are trying to connect to the Internet using another method, see the documentation that came with your Internet account.
-
Choose Apple menu > System Preferences, then click Network.
-
Click “Assist me,” click Diagnostics, then follow the onscreen instructions.
If Network Diagnostics can’t resolve the problem, there may be problems with the ISP you are trying to connect to, with an external device you are using to connect to your ISP, or with the server you are trying to access.