I have a problem!

I finally decided to post about it, because it just happened again

Jasper sometimes chases and jumps on the smaller pups and the cats.

Whenever he does it, I make him sit and I tell him no or put him into another room for a little bit, but it's obviously not working.

I know he's trying to play with them, but they are alot smaller than him and I don't want him to seriously hurt them someday

Any suggestions?