Modem > VOIP adapter > router
It's actually the preferred method since VOIP will be given priority over other traffic, and call quality won't be affected by high internet use. Just be sure to configure the network devices properly.
Question: Can a VOIP gateway device be connected between a DSL or cable modem and an existing wireless router? Here's my problem. The cable and phone lines come into a box in the garage, that's where the cable modem is. But my wireless router is in the attic on the end of 50 feet of CAT5 cable. I want to add a VOIP modem, but want it in the garage where the phone lines are. It's not convenient to bring a second CAT5 cable back to the box from the wireless router, so can the VOIP modem be connected inline with the router, or in parallel (Y-cable) with it?