When you set up local networks, the firewall assumes that these are on the internal network. You can also set up routes to external networks that are behind the default router, if this is necessary. To do this, you need to create or edit the file /usr/local/custom/route.out. This file can contain entries of the form:
network-address address-mask gateway-address
The firewall will add static routes to each network specified in this file, and then the proxies and transparent gateway program will be able to access hosts in these networks.