Just to add my experience, not saying this is the right way or the wrong way but it worked for us.
We rescued a 12 week old rotti x collie from Many Tears and at the time had 3 bunnies in the garden in hutch/run combination. The first time we went into the garden we had max on a lead, this tells the dog your in charge for starters plus we can stop any bad behaviour. As soon as we stepped out of the back door we kept our voices very low and gentle and reassuring. We let max go up to the buns and sniff them, if he showed any sign of wanting to play with them we distracted him with one of his toys. We carried on doing this till he wasnt interested in them in their runs.
Next step was free ranging, when I am here at home the bunnies go on a rota system free ranging. Again we took him out into the garden on his lead and talked gently. If a bunny came up we would try and get him to sit, also we used the words....be gentle. Ok so he didnt know what it meant but he could tell by our tone. If he let the bun come up and sniff him without him wanting to play he would get a little dry biscuit treat.
He is now 2 and 1/2 years old and is very good with them, it took some hard work and to keep on but now he shares his living room with 2 oldies who are in an open pen. Some people would say this is irresponsible, be it on my head, and yes you cant trust them 100% but the interaction between bunny and dog is amazing. He even sometimes drops his teddy bears in the pen as if to say....here, would you like to play with them with me.
Be firm and be in control. I was commended the other day by a dog walker for Max being so obedient, I told the woman it took a lot of effort on our behalf. We dont use violence, we do use stern voices but also we give lots of controlled praise. It works but there again having a rottie you need to be incontrol. 35Kgs of power!!!!
