Well, after my bunny, Ookpik, was litter trained, I just opened her door and let her out. My cats showed some interest and went to sniff her, and that's all they've done to her. One thing about my rabbit is that she's very in your face and sort of pushy, rabbits don't see well close up so she likes to push things and sniff them good, my cats don't like to be near her at all. But it depends on your rabbits personality. Most people with cats and rabbits don't have problems between them, at least I haven't come across any. I should also mention that my cats are hunters, especially Missy, she's killed grouse and dragged them home before. So of course I was concerned she'd see Ookpik as supper, but not so, maybe they know she's part of the family? I let my rabbit free roam most of the time and the only time there's aggession is when one of the cats goes into her cage, lol. We have quite the menagerie and everyone is pretty easy going and gets along. But only you know your cats and bunny. Let your rabbit out for her/his free time and let the cats wander in under supervision and see if they're all right together.