I have never set one of these up before and need a little assistance. Right now we have a T1 line coming in from Sprint to a Cisco 1841 and then on to our router. However, when I plug the Cisco 1841 into Port 0 and the router into Port 3 it does not work. In Port 1 I have my management computer plugged in. We have one subnet and this must be easy but I cannot figure out how to make this work. When the firewall is plugged in then I get no internet or network access.