You enter a default gateway and the gateway disappears, not even after a reboot – it just disappears in a couple of minutes.

Open up by going from “START > RUN REGEDIT” > Press Enter

Navigate to the following key “HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces”, select the interface that is missing the default gateway. You can tell which interface by the IPAddress entry. Create a new STRING value in the selected interface key.

Type: STRING (REG_SZ)
Name: DefaultGateway
Value: enter the IP Address of the gateway; in this case it was 192.168.11.2

Open the properties of the network connection and you should not see the gateway listed, after I did this I did not have any more issues with the gateway disappearing.

Reboot.