Cats and dogs can live together peacefully. The thing is, they don't always live together peacefully. There's plenty of things that can go wrong in the cat/dog relationship. For now, let's talk about what to do when the cat picks on the dog.
Cats like to skulk and pounce and swipe. This mighty predator kitty show is quite charming. That is, until all this taunting and zooming has left the poor dog unable to move around in his own home without being ambushed.
Take action before it comes to this.
The cat jumps on the dog because it's fun. One thing you might try is playing with your cat, then perhaps he'll get his fill of fun, leaving him no need to torment the dog.
Some say squirting the cat with water deters bad behavior. From what cat owners trying to keep kitty off the kitchen counter or out of the house plants tell me, the squirt bottle system doesn't work very well. At best, the cat refrains from the designated bad behavior only when you are present. This will help the long suffering dog only if you keep dog and cat separated when you are not watching.
You can anticipate when the cat is about to attack the dog. The cat will arch his back, lower his head, and may get a determined gleefully hostile look in his eye. Yelling NO at this point won't do much good. (It works with dogs. Do dogs have a conscience and cats don't? Are dogs more inclined to be respectful of authority? Is it that cats think they are the authority? Thorny questions to be explored another time...)
You can do something before kitty leaps onto the dog. Distract him. Step in before the cat takes flight. Engage and entertain this energetic feline. Offer a toy on the end of a stick, for instance. The cat can deploy his killer instinct by swiping at a stuffed fish rather than Rover's tender hide. Help the cat release some of that vigor with other toys, a new scratching post, or invest in one of those cat rigs with the tunnels and planks to run on. Even if you live in a small place, you can find room for a cat's amusement park by placing it up high. Cat's don't generally fear heights! Just be on the look out that kitty doesn't use his new improved higher perch to banzai the dog. That would make you sort of an enabler. Just to be on the safe side, consider arranging for ways that the dog can avoid the cat when you are not there to referee.
One other suggestion. Maybe the cat needs his chin rubbed or a chance to sit with you on the couch. Is the dog the only one getting petted? Could be the cat just wants more attention from you.