At home I have two computers, in two different rooms, both with internet access. My main computer is connected through a router that is connected to a cable modem, the cable modem is also connected to a switch that connects to a second router that connects to the other computer (the other computer has a printer). Computer 1 is connected to the basement hub. The cable length is approximately 14 feet. Hub to Linksys router about 25 feet. Linksys router to second computer about 12 feet. IP address of 1st computer is 192.168.123.101, the IP address of the second computer is 192.168.1.100. How can I use the printer on 2, from the first computer or is it possible?
-- Ron Hughes

Yes, it's possible, but it'll take a bit of work. To be able to print from computer 1 to the printer attached to computer 2, you will need to put some access rules on the router that has the computer with the printer on it so that it will accept traffic from your other router and be able to send traffic back. This may require some access rule on the router where the computer is that is trying to do the printing depends on the firmware in routers handles incoming traffic. You will need to configure the printer on computer 1 by using computer 2's public IP address on the router it is attached to.

There's another option, if the routers both have VPN functionality. If so, you can build a tunnel between the two routers and then print to the printer from the other computer using the local (192.168.1.100) IP address. Depending on the firmware, configuring the VPN might be a little tricky if you're not used to doing it.

With either of these options, I would suggest getting a USB print server so that you can print to the printer from computer 1 without having computer 2 turned on.

But wait, there's another option, and it might be the easiest to set up: Consolidate your current network configuration to a single router. Replace the cable going from the cable modem to router 2 (that now connects to computer 2) with a cable running from one of the LAN ports on router 1. This will give you a local address for both computers out of the same IP address range, reduce the number of routers/firewalls that you need to maintain and make printing from either computer pretty straightforward. If running a new cable isn't an option, you can put a switch/hub in place of the current router 2 - with the caveat that this will add another point of failure. If you do pursue this route, however, make sure the switch/hub you install has auto MDIX ports that will automatically compensate for having to swap the transmit/receive pairs - so you don't have to rewire the RJ-45 connectors with a crossover wiring.