I have two separate Internet connections connected to a Mac and I'd like one of them (via Ethernet en0 gateway) to serve for just backing up to an remote online storage, and the other one (via Airport en1 gateway) for all other Internet traffic.
I tried using "route" from the terminal as follows:
sudo route add -host 188.8.131.52 -interface en0
(just for testing against the site www.whatismyip.org whose IP is 184.108.40.206, to see through which gateway the traffic is routed)
I can see using netstat that the route is added.
However, the traffic in this case does NOT get routed properly through Ethernet, as if the routing definition I made is ignored.