Route issue

[pirho]

I have a mac Mini with a USB ethernet adapter, plus the built in WiFi, and Built in ethernet. The USB adapter is on a completely different network then the WifI and Built in are (USB is on 10.95.5.x/24, wifi is 192.168.1.x/24). On the 10 network I need to reach devices that are also on multiple networks in the 10.x range. I add the route statement to the mac via terminal (sudo route -n add -net 10.0.0.0/8 10.95.5.1) and I can reach any 10 network that the default router knows about. Problem is the traffic does not get segmented the way it should. I constantly wind up dropping packets reaching anything on the 10 network, even if I set the service order so the USB adapter is the first connection in the list. Only when I disable the other interfaces does the 10 network cleanly respond. Is there a way to force all traffic for that USB adapter out that interface that it is actually set for? It looks like the Mac is attempting to load balance the connections instead of rout them out the proper ethernet. Currently running 10.11.6