Make sure you do the introductions right or you'll be asking for trouble, our Doberman chased cats from day 1 and never stopped, it was awful. I'd recommend crating the dog and letting the cats come to him. Always make sure the cats have an escape route too. Prase the dog for nice behaviour, distract the bad.
My jr x and cat live side by side by a mutual understanding, the dog chases the cat when he gets the opportunity (usually in the garden when the cat is not on guard!) and in return the cat will attack the dog in his sleep. Generally it goes something like:
Dog: omg omg omg it's CAT im going to sniff it and lick it and kiss it...
Cat: (unmoving) f*ck off.
Dog: I will love him forever and make him my squishy
Cat: (still unmoving) seriously dude, f*ck off
Dog: omg omg omg, it's still a cat, oops. I just peed a little
Cat: launches into a vicious attack, involving scratches to the nose, then returns to original position.
Dog: ooooowwwwwww. Whaddya do that for? I was only being friendly.....
And repeat. Twenty times a day