Problems with a SPARC 5 and Qwest DSL Modem

I have a SPARC 5 that I have put a second NIC into because it will become an
internal router for a business that will be the only route point out to the
Qwest DSL modem. I have tried and tried to get the SPARC box to talk to the
DSL router with no luck. Right now I put all the internal computers on the
same subnet until I can get the SPARC box to talk to the DSL router.

The problem: I can ping every computer on the network, except the DSL modem.
Yet all the other computers can ping the DSL modem. All the other computers
are Windows boxes and the SPACR 5 is running Linux 2.2. Has anyone seen this
type of problem before or have a clue as to why the SPARC Linux box can not
ping the DSL modem, yet all the Windows boxes can?

I would like to have the traffic go through the SPARC box so I have a better
security point for the business.

Thank You,

David Demland