The default gateway is the private IP address of your router. I have upgraded my surface pro from Windows 8 to Windows 8.1 and just get the problem with internet keeps dropping randomly and the wireless network is limited. I ran the troubleshooter to make a diagnostics and it said “Default gateway is unavailable”.
I try a lot of methods, such as reset the WINSOCK, IPv4 TCP/IP stacks, and clear the DNS resolver cache, but that doesn’t take any effect. Then I configure the TCP/IP settings manually and it still disconnects every 5 minutes. Pinging 184.108.40.206 says request timed out, and I think it is not the ISP’s problem.
Finally I notice that the network adapter’s driver has been corrupted after the Windows upgraded. The solution is to re-install your network adapters driver.
* From Start Screen, right-click the lower left portion, and select “Device Manager” from the shortcut list.
* Locate the Network adapters and click on the Flag button to expand. For example, I am using the Linksys AE3000. Right-click on the Linksys adapter, select Uninstall, check “Delete the driver software for this device” and click OK.
* Now go to your manufacturer’s website and download the related
driver for network adapter. Install it and then restart your tablet or computer.