Our internet connection comes through our garage via cable modem and then goes into a router. There is a computer in the garage that plugs into that router. The Ooma is in the house on a second cable plugged into the same router. Our main computer is plugged into the Ooma. My problem is that the Ooma is creating a secondary network and is not letting our main computer share files and the printer with our garage computer.
How do I configure the Ooma to keep it from creating a secondary network? ...or at least allow the two computers to share files and printers again? I would prefer not to have to by a switch or other additional equipment.
When the Ooma device is placed behind (on the LAN side of) the router, most people plug nothing into the home port of the Ooma device, for the reason that you just gave.
You could run another cable from your router into your home, or add a Switch to your LAN configuration. A switch is a network port multiplier. The network cable that is plugged into the Ooma device can be used as a feed and be plugged into the switch. Than you can plug your computer and Ooma device into the switch, plus other network devices that you might want to add later, up to the number of remaining ports that you have. The switch will distribute same LAN, router IP addresses. Than you will be able to use the two computers and share files and printers again.
An eight port switch that I like is a Cisco SG 100D-08 8-Port Gigabit Switch.
But there are several other switches out there including four port switches.
Without purchasing a switch, I would have to run about 50' of cable through the attic. Can I do this via configuration only? I really don't want any more equipment on our desk.
You can use this to send two 10/100 internet connections over one LAN cable.
One goes at each end of the cable. It uses the unused wires in the cable to provide the second connection.
I haven't heard of anyone doing what you want.
There is software that you can buy to install on both computers. But the software would probably cost more than either the Network cable or the Switch. And I don't think you'd be happy with the software.
For me I'd purchase a switch, because than you'd take care of your present problem, and would have room to add more network devices later.
There is no way to turn off the DHCP server in the Ooma, which is creating a separate subnet. However, if you configure DHCP in your router and DHCP in the Ooma to assign IP addresses that are not duplicated but are in the same subnet, the problem may be solved.
For example, configure your router to assign 172.27.35.100 through 172.27.35.120, and the Ooma to assign 172.27.35.121 through 172.27.35.140. Note that these two ranges are in the same subnet and must not overlap. Or similar ranges in the 192.168.0.x. This may solve your problem without additional wiring or hardware.
I have not tried this, though. Depending on the firmware in the Ooma, it may not work at all, or may require that you also set up some port forwarding. But it's something to try.