Modem not passing port 515

[ValleyCityPlating]

I have a SMC modem. I have port forwards set up for RDP to certain computers on the network. I also have a zyxel firewall that has been setup for the RDP as well. Currently the RDP works correctly, but I'm trying to port forward port 515 for remote printing. I have matched the settings on both the modem and the firewall to the working RDP settings but the modem appears (per the logs on the firewall) not to be passing the info. I am wondering if setting the modem to true bridge mode would help. I have reached the extent of my knowledge on what to do. Any help would be appreciated.

[VBSSP-RICH]

Hello ValleyCityPlat... and welcome,

What is the IP address of the device that your are trying to port forward port 515 for?  

You can only port forward ports of a device that is using any of the SMC Gateway DHCP IP addresses.

Look forward to hearin from you.

[ValleyCityPlating]

10.1.10.10. It's forwarded to the firewall.

[VBSSP-RICH]

If you are using a FireWall (FW) device, then you should have one static IP address that your FW Wan network interface should be programmed to. If you are using the  Comcast Gateways (CG) internal DHCP server, then you will have real difficulty with using 10.1.10.10 is this is within the range of dynamic IP addressed being doled out. I would advide you to change your FW address to 10.1.10.5 and also change the CG DHCP Leasetime=Forever. This should work for you and you should be able to port forward that port to the 10.1.10.5 IP.

Hope this helps you out.