The puppy needs to learn his boundaries around the cats very quickly. When we got our puppy last year, he came from a litter of 11 and viewed the cats as his littermates and tried to play with them as such. Since he was a big puppy, this was not well received by the cats, as puppy play involves wrestling, biting & nipping and general tackling.
To set his boundaries we kept constant vigil with him and simply redirected him to his toys each time his behavior got out of hand. The vigil also helps in potty training and inappropriate chewing. We also spent a lot of time playing with him so that he had someone to play with. Time outs in the kennel are esssential at that age. We ended up adopting one of his brothers 30 days later to give him the added stimulation that he needed (he is a highly active breed). He's left the cats alone since then.