We have 3 dogs and 3 cats in the house. Only issue is keeping the kitty boxes blocked away so the dogs don't visit the buffet of treats the cats leave behind.
Kaiser is learning that if he approaches the cats slowly they'll tolerate him right up until he gives them a nice slobber lick or he gets to aggressive with the sniffing.
We don't have any issue leaving them all together. But the cats have their towers and the upstairs is blocked away from the dogs when we aren't here. So the cats can hang out upstairs without the dogs, but they are all generally down stairs together.
Kaiser Von Crybaby Met Tsunami (GSD)
Hawk Nom Nom Nom (Boxer)
Sparkles That Is Your Majesty To You (Boxer)