We just purchased an NSA 240 for our small office. Unfortunately, despite my best efforts, I must be missing something big. I've tried several different things but the packets just won't travel.
Let me explain how we've got things set up - first, the line from our ISP comes in to the cable modem. The modem has its own built-in routing and firewall, etc, but that's all disabled. The modem feeds into a small Linksys router/wireless point. That's where we've got everything built. We're using its firewall and NAT. From there, it goes over to our switch, and everything is golden.
I was advised to deploy the firewall between the modem and router. While reading through the documentation for the NSA 240, however, I noticed one of the deployment scenarios involves using the firewall as the gateway, with no other gateways involved (i.e. modem -> firewall -> switch). I'm beginning to think I took a wrong turn here by not setting it up like that.
I set up the NSA 240 without too much trouble, copying over the existing port forwarding and IP addresses. I entered our public IP as the WAN on the firewall, and the local IP of the Linksys as the LAN. Similarly, I entered the local IP of the firewall as the WAN for the router, with its gateway as the LAN.
After applying these changes, unfortunately, I was then unable to get out to the internet. All of the computers were still visible to each other locally, and still were being given IP addresses by our DHCP server, but I was completely unable to get beyond the firewall. This leads me to believe I've made at least one, and probably several big errors here.
Hopefully you fine people would be able to steer me in the right direction. I know I probably got the public/private IP allocation wrong somewhere, and I'm still nagged by the thought of making the firewall itself the gateway.
Lastly, if I go with the "firewall as gateway" scenario, I'll unfortunately still need the Linksys in there somewhere, to provide the WWAN (we don't have the wireless module for the NSA 240). If I wipe all the settings out of the router, will the two devices be able to peacefully coexist?
Thanks in advance for any light you'd be able to shed on this. I've been at this job a whole two weeks and I'd dearly like to continue being employed.