Need some help from the greater experts on what I'm doing wrong here. Here's the scenario:

Office LAN with two gateways (one DSL, the other T1), each protected by an older SonicWALL hardware firewall.

Just purchased a new SonicWALL TZ 170 to review for possibly replacing the old SonicWALL units.

So I have a test box set up in my office that's connected to our LAN. I plugged the SonicWALL into a switch here in my office that's connected to the LAN and placed the test box behind it.

The SonicWALL has successfully receive both a WAN and LAN IP, so it looks like all the connections are working well.

Configuration isn't set yet to block any traffic.

But here's where it gets wierd:

The box behind the TZ 170 cannot ping any other box on the network. Likewise, no computers on the LAN can ping the test box behind the firewall. In fact, they can't even ping the firewall itself.

The firewall, though it shows itself as being connected to the WAN, cannot connect to the Internet to download updates and whatnot. I get the message "DNS lookup failed, please check your DNS server settings".

So, two questions:

(1) What could I be doing wrong? It sees the LAN, sees the WAN, but no connection to the outside world or any other machines?

(2) Would this problem disappear once I connect it directly to the router? Will that make things easier?