Aggression or Not?

[Eric]

I have an 11month old intact European gsd named Gunner. I'm not sure if he is displaying territorial aggression or just excited. In my backyard all of my neighbors have dogs. There is a break in one of my neighbors fence were his Australian shepherd can peek through and probably get through if he wanted. That dog also barks all the time. Gunner knows he's there, might go over to say hi but never barks at him. But he usually doesn't even pay attention to him. Another neighbor has a boxer (i'm not sure if he's neutered) that never barks. If Gunner sees him out (it’s a vinyl fence were he can see a little through the cracks) he goes crazy. Jumping on the fence, barking uncontrollable and his hair up on end.

If I'm inside, I bring him inside quickly. If I'm outside, I've try to use his Frisbee (he's toy motivated, not food) to distract him. I get him to sit, knowing the other dog is still there and only through it when he stops barking.
So my question is, is this territorial aggression or something else? And if it's territorial aggression how do I stop it?
Thank you,
Eric

[Emoore]

That's so weird. My neighbors on one side have two female GSDs that bark all the time and stick their heads under the fence. My dog completely ignores them. My neighbors on the other side have an older boxer who ignores my dogs and never barks. My dog HATES that boxer! Anytime he sees him, he'll run over to the fence and bark at him, while the boxer looks the other way.