I have wasted a complete afternoon thinking my mac or my router was broken whilst trying to solve this scenario:
Setting up a raspberry pi 3 with a completely new OS (raspbian jessie lite). The pi was hooked up via ethernet and I tried to access it over my mac with SSH and a 192.168.x.x ip that was correctly assigned to the pi via my router. And, of course, I was in the same network as the pi. The ssh connection returns with
I am only writing all this down because I am furious for not having found the answer earlier and in the hopes that someone who might have the same issue gets there quicker!