client1% route add 10.10.10.1/24 20.0.0.100 client1% route add 11.11.11.1/24 20.0.0.100
In this example, all client initiated traffic with a destination IP addresses of 10.10.10.1 or 11.11.11.1 will be forwarded to the gateway interface 20.0.0.100.
client1% route add 192.0.0.0/24 20.0.0.100 client1% route add 192.1.0.0/24 20.0.0.100