On Windows Server 2012 R2, the default gateway is set, but ipconfig shows it set to 0.0.0.0 as the first gateway, then the actual gateway as the second.
To fix this, run this command: route delete 0.0.0.0, then set the gateway again.
The incorrect 0.0.0.0 gateway can also be set by Adobe’s Bonjour Service, which you can fix by disabling that.