Mac Network Issue

Recently, one of my friends asked me to help her to resolve her MacBook Pro issue. She brought in a MBP from oversea. It was working fine when she was oversea. Then it stopped connecting to internet or any network devices through either Ethernet or Wifi when she was back to Canada. She was using local mobile network router when she was oversea. In Canada, she uses Airport Extreme Base Station.

I tried to use System Preference to reset network and tried to reset Airport by Airport Utility. The Wifi was detected, but the MBP could not connect to Internet.  The Ethernet cable was connected but it could not make any network connections. I also tried to reboot the system. It was dead locked.

The Solution

Then I went to web to google solutions. I was lucky to find a solution in short time. Here I repeat it again for future reference.

Delete SystemConfiguration folder in root preferences

1. Open Finder.
2. Press Command+Shift+G shortcut key.
3. It will open a dialog of "Go to the folder". Type in: "/Library/Preferences/SystemConfiguration" (without quotes).
4. The Folder will open the folder of SystemConfiguration.
5. Drag this folder to your desktop.

This actually copies the folder to Desktop as the original backup. If the following steps are successful, this folder on Desktop can be moved to trash.

Remove Airport entries in Keychain

1. Press Command+space to open Spotlight. 
2. Type in: "Keychain Access" (you may see it while typing. No quotes).
3. Select Keychain Access and hit Enter key.
4. Keychain Access app is opened.
5. Select your default keychain. ("login" is the default if you have not changed).
6. In the spotlight search area, type in: "airport" (no quotes)
7. A list of entries of Airport... is displayed.
8. Select one and press ‘delete’ on your keyboard.
9. Repeat above step to delete all of them.
10. Select "System" from the list of Keychains.
11. Repeat steps 6 to 9 above.

Restart Your Mac

Restart your Mac or MBP. Now you should be able to verify your network connection from System Preference. If the Ethernet is in green, that explains your local network is OK. Try Safari to test your Internet connections.

Reference

• Jamie Starke blog: MacBook Pro unable to connect to internet after waking from sleep