Comment 31 for bug 438454

Alexander:

Yes: changing that manually to never-default=false, and disabling, then enabling the interface, sets the default route.

So 'false' should be the default, which works for the primary interface. I don't see a GUI setting for selecting that - there should be one, as one doesn't necessarily want a default route on secondary interfaces.

Thanks for finding that!

So the problem is basically that the dialog doesn't allow one to set this; and the default should be 'false'.