I have the configuration shown below. I also have a software router (IPNetRouterX) that I trust. It is kept current via periodic updates. My current setup has IPNetRouterX on the Mac Pro. The Internet modem is connected to built-in GbEthernet Card 1. The Mac Pro is connected to my LAN via built-in GbEthernet Card 2. I have two GbEthernet switches that service the LAN that includes one additional Mac, a Dell XPS, an IBM ThinkPad and an HP4200n printer. The physical layout makes two switches desirable. I have connected the Time Capsule to the network via a cable from the first switch to the WAN port on the Time Capsule. This allows me to back up Time Machine over the GbEthernet network. It works very well. I also am able to do a scheduled backup of a SuperDuper! sparse image of the system every night. The sparseimage is in its own folder that coexists with the TM sparsebundle on the Time Capsule's hard drive.
The downside of this arrangement is that I can't get Airport Extreme to connect wirelessly to PC Laptops when our children come to visit. Everything worked well (both LAN and wireless connections) when I used Time Capsule as a router by connecting the cable modem to TC's WAN port and connecting a cable from one of TC's GbEthernet ports to the first switch. This requires me to abandon my beloved software router. My question is: Is it mandatory to use TC as the router in order to provide laptops with wireless connection to the Internet? I've not tried the Guest Network option. For a networking newbie, the manuals don't make the answers clear, IMHO.
