Emerald :
I have done one of these setups before and the way I did it is:
1) assign 192.168.5.1 as a LAN IP to the WRT54GL
2) assign a Static IP to the WAN of the WRT54GL
3) connect the printer to the WRT54GL and assign it a Static IP like192.
168.5.10
4) port forward port 9100 (for HP printer) to the printer IP 192.168.5.10
5) on the main network on the computers that need to print to the printer attached to the WRT54GL change the printer port to the WAN IP of the WRT54GL
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Additional information for my problem:
I have two AIO machines, 1) an HP Officejet 6500 E709a Series with a static IP used as a printer and scanner and 2) a Canon iR-ADV C5030 also with a static IP used as a printer, FAX and scanner. The RAW port for both is 9100. There are 12 PCs throughout the complex that need to use one or both of these, plus any visitors. I haven't done any port forwarding before and I'd really prefer NOT to have to change printer setups on all the PCs. In your scenario, does the second router (wireless) have DHCP on?
I have tried connecting the printers to the wireless router (DHCP off) without port forwarding (due to the perceived RAW port conflict) and the visitors can use both. The visitor(s) cannot see the fileserver, so that part of the requirement works great! However, none of the wired PCs can use the printers!
Does anyone have a clean (not needing to update all PCs) solution to this problem?