Has anyone built fences around their whole settlement so it is confined, like Megaton? If so, how does it work?
When your settlement is attacked, do you actually see it happen or does it always happen when you are away, and your defence success rate depends on your defence rating? Since erecting fences around the settlement doesn't increase the rating, it would be pointless.
Or can you actually see it happen and help your settlement out, and the fences actually do a good job in keeping them out?
However, is it possible for the fences to do too good of a job, and therefore it becomes boring as no attackers can challenge you?