Hiding An IP Route

I have a NetWare 5.1 server with 3 segments. One segment attaches us to our corporate WAN, the other two segments are for our internal network. I am using BorderManager 3.5 for Internet/Firewall services. I do not want the Internet route to be broadcast over the WAN. Is there a way I can configure the NetWare server (or BorderManager server) so the Interent route is not advertised over the WAN?