T1 and DSL, same switch, DHCP + VOIP… is this possible?

Question

Need a little advice/help here. We're trying to use two separate Internet connections, through a single switch, with static IP for the T1 and DHCP (using a router) for the DSL. But we are also trying to keep file sharing, network printing, and VOIP phones all working.

I have included a diagram with how we're trying to set our office up, and I'll be more specific with what we're trying to get working:

A. T1 line, connected to a switch, with each PC in the office connected to the switch for Internet access and file sharing. (blue line)

B. DSL line, connected to a router, connected to the same switch. (green line)

C. VOIP phones, connected to switch, using DSL through the router with DHCP (green line)

D. All PCs able to print to printer that is connected to switch. (pink line)

All the colored lines represent exactly how the network cables are run. The only exception is the PCs - the PCs are connected to the VOIP phones, and then the phones connect to the switch - one cable between each device for everything.

In simple terms we're trying to keep our network functionality (file sharing between PCs, internet access, and printing to a central printer) / we're trying to keep our VOIP phones working / We want only the PCs to use the T1 for internet access / we want only the VOIP phones to use the DSL.

So far we haven't been successful. We're not sure if it's a settings thing, a hardware thing, or other. Is this even possible, or do we need different hardware or a different configuration?

We're not exactly network experts beyond home setup, either. =X

Answer 1

Your infrastructure switches should support separating phones onto another vlan. Then place this vlan for phones in the appropriate place (trunking or not). All other data is on a separate vlan and goes out the other interface.

Answer 2

First off, look at edgewater for a good solid router that will take a T1 and supports Vlans with quos and traffic shaping to ensure good quality voice. Second, if you insist on having a DSL line too, you're best off using a load balance or fail over device to manage both incoming WANs - using a switch with two routers like that is a bad idea and probably won't work without extensive work-arounds that will cause you nothing but headaches.

EDIT: It would be better if you used something other than copper for a secondary line, such as cable, as it will keep your network up when something goes wrong at the CO you're connected through.