We have one dog who came to us as "cat safe", but was truly barely "cat tolerable". We worked consistently with the phrase "no kitty" anytime there was any interaction that could be remotely considered inappropriate. It took four or five months, but he is much more reliable than ever before. The reality with him, though, is we can never be sure he won't turn on them. Interactions are supervised and the cats always have a safe place they can go. It definitely helps thata I work from home, so someone could be with them most of the time to monitor their interactions.