It depends on what the dog is trained to do, for example if your buying a puppy that comes with the regular puppy training the dog is just trained to be obedient and not aggressive at all. But with a dog trained in protection that’s entirely up to you. Some people choose to have their dog react to anyone at the door, while others prefer their dog to be accepting to anyone who enter unless told otherwise. Once you communicate to your dog that it’s OK, your dog will gladly accept your family and friends into your home.