We have an 11 month old Lab who is well trained in every way except this one. Our cat was curious when she was a small puppy and we made the mistake of encouraging their interaction instead of teaching the dog to ignore the cat. And unfortunately the cat isnt the type to give the dog a swipe and assert dominance. He doesnt even do it with other cats! As the dog has got bigger, the cat has become more and more wary ( unsurprisingly) and now really only comes in at night. We feed the cat upstairs and there's a stairgate so he can be completely separate from the dog. The issue is that on the odd occasion when they do meet, the dog gets really excited and runs up to the cat, the cat runs and the dog chases.
I can't see any way of training her out of this as it doesnt happen often enough and is too unpredictable to be able to reward her for ignoring the cat.
The dog is very intelligent and has been easy to train in every other way - I would really like some advice about stopping the chasing.