Setting a Non-Persistent route in OS X
From a terminal:
sudo route -n add 172.168.17.0/24 192.168.1.27
Where 172.168.17.0/24 is the network and 192.168.1.27 is the gateway
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From a terminal:
sudo route -n add 172.168.17.0/24 192.168.1.27
Where 172.168.17.0/24 is the network and 192.168.1.27 is the gateway