I am bit out-of-touch with 7-mode stuff, but as I remember, the routing table uses the default route when no other known route exists for a given packet's. But, you can add static route to for the destination using the following command.
How to use the route add command
To add a route to the 10.17.250.0/24 (or whatever destination) network via 10.17.250.1, use the following syntax, using the proper value for the metric:
filer> route add net 10.17.250.0/24 10.17.250.1 1
Put that command in /etc/rc, else you will lose this route on a reboot. /etc/rc gets read at boot and sets up your network settings.
Copy all the text that it outputs, past it in a notepad, add the above command below the route add default, and write it back.
paste the edited notepad stuff.
This command overwrites the file with everything you enter at this point.