[Ayoka]

I'm not 100% sold on the scruffing technique as there will come a time when you can't do this (either the dog won't stand for it or he'll be too heavy to pick up) and I also wonder if it wouldn't make a puppy hand-shy...everything you do to a young dog can have a lasting effect on them so I would lean towards less physical methods.

We Brought Bear (at a year old) into a home with 5 cats..now there's just 2...we provided the "no dog zone", which was essentially the top 2 floors of the house...and now when Bear get's too pushy with the cats, they are VERY good at letting him know they have had enough and he has a healthy respect for them (and their claws).

Your puppy is exactly that, a puppy, so create a dog free zone and keep a leash on him when the cats are near so that you have some control over what he does and does not do. When he goes for the cats, "say leave" it and then distract him with something else like a good treat or another toy...hopefully he will make the connection but many dogs just can't live with cats, their prey drive is too high. All else failing, you have to be prepared to keep them seperated. For life.