Dogs are weird about who they bark at and who they don't. I have a cattle dog who is insanely protective of me. He won't let anyone come within about two feet of me, even if he knows the person. However, here's what I have found. If someone knocks on the door - he goes insane barking and continues to bark even after I let them in and he knows that person as someone who he is very familiar with. However, anyone can open my door and walk in without knocking and he doesn't make a single sound. In fact, it takes him a minute or two to get up from his nap on my bed to come and see who has come in the door. Regardless of who it is, HE DOES NOT BARK if the person just opens the door and walks in. He only barks if they KNOCK. I think the reason he doesn't bark when someone walks in, as opposed to knocking, is because he thinks it must be me. However, if I open the door to a delivery person - DoorDash, Instacart, anyone - which I do when I see them coming to prevent him from going crazy if they knock. He still goes insane protecting me. He will bark at them, growl at them, charge them, he has even gotten past me and chase several of the delivery people away. I know in that instance he is protecting me, but I can be sitting in the living room and someone can walk in (that I know) without knocking and he does not make a sound. It's so weird.