home network planning with all-linux questions

[Tom Poe]

I have multiple boxes to connect.  I want one to use for VoIP/PBX, one 
for workstation, and one for router/gateway between LAN and DSL modem.  
The router/gateway has two NIC cards?, or can I use just one card with a 
virtual configuration?  I'm also looking for a beginner's article that 
walks me through steps to set up network to have both VoIP/PBX and 
workstation have access to Internet through the router/gateway.  I can 
find pieces, but nothing that makes it come together for me, yet.  Any 
help appreciated.
Tom