You will need to setup the default route for all Internet traffic on your unlocked
path.
The trick is to explicitly setup routes for all the end-points reachable only on the locked
network to use the interface wired to that.
On the comment.
I am assuming that you have a dual homed host with internal and external networks wired to two different interfaces. For that the interface selection has to be done on the local host.
But, if there is a single interface path to the router appliance which splits two ways (the locked and unlocked network paths), you need to setup such routing on that device.
which platform? – fretje – 2009-08-07T17:29:33.293