I have a similar problem. Attached are my notes / query.

Summary: can't print to Dell 3100cn printer over a WAN router-to-router

Symptom
Dell 3100cn color laser printer, with the latest firmware installed (August 2006),
is NOT listed on the Netgear FVS318 Firewall Router on the router's
administrative webpage "Attached Devices" list

Question
how to get the Dell 3100CN listed as "attached" on a Netgear FVS318 Router?

Impact -- ok for LAN local printing
This does not affect printing on the local LAN. That works OK.
Visiting the printer's IP address shows the Status webpage OK.

Impact -- Problem on WAN remote printing
It is a problem on WAN (Wide Area Net) printing via router-router connections.
The local router on which the printer is physically connected does not see it as attached, and does not route the packets.

the Dell 3100CN's IP is on a fixed (local) IP address,
similar to 192.168.0.6

I tried default configurations, with no routing rules.

I tried adding various routing rules, e.g. sending LPR protocol to that address.

I tried putting that address into a DMZ.

Nothing happens.
Remote systems do not see the printer.

The router-router connection works OK.
We have another printer connected. It is listed as attached, and works fine.
(Brother 8840DN)

Also tried having ONLY the Dell 3100cn connected to the Netgear router.
Nothing else connected. Rebooted the routers.
Made no difference, Dell 3100CN was not "attached".

PC's are Windows XP with SP2, all the latest updates via microsoft.com

Windows printer driver uses the 192.168.0.xx addresses.
Does NOT use the external WAN IP address.
Does NOT use rules to send port 9100 traffic to the printers.

Dell 3100cn is not listed as "attached" even when it is the ONLY printer cable plugged into the FVS318 and the router is rebooted.

same behavior happens both when the Dell 3100cn is "ready" and when it is in "sleep" mode.

Tried setting the IP address for the Dell 3100cn as a DMZ port, same problem.

all help appreciated!

Thank you!