I know my question is a bit vague. Read on.
I have a static route set in my Asus router to bridge from one subnet to another (downstream router). My Mavericks machine can connect to devices (via a web browser pointing to a devices' IP address control panel; for instance, a Brother printer) on this other subnet just fine but all (and I've tested 4!) Yosemite machines cannot. I have also found that a Windows 10 machine connects just fine. These Macs are all connected to the main router via wifi, DHCP and all options in network settings appear to be identical. It appears to me that something changed in Yosemite. btw, ping results via Terminal are basically identical on Yosemite and Mavericks. 0% packet loss to one of the intended targets and 100% packet loss to an unused address in the downstream subnet. The only differences are just some expected variations in the ping times.
I have also found that a Lion computer (10.7.5) can also connect to the other subnet just fine. Do I have something screwed up or is there a problem with Yosemite?