Hardware needed for home network

[Jason Hsu <jhsu802701@jasonhsu.com>]

I'm in the process of setting up an old computer as a firewall and server.  It needs to connect to my DSL modem AND my main computer.  However, this old computer (like every other computer I've had) only has one Ethernet port.  I know this is old hat for many of you, but I've never done this before.

What do I need to connect my firewall/server computer to a DSL modem AND another computer?  I do use an Ethernet cross cable to connect my main desktop computer to my laptop when I need to transfer files.  Since the Ethernet port of my laptop no longer works, I have to use a USB-to-Ethernet adapter.

If I use a regular Ethernet cable to connect the firewall/server computer to the DSL modem, would it work to use an Ethernet cross-cable and USB-to-Ethernet adapters to provide the connection to my main computer?  Are there USB-to-USB cross cables?

-- 
Jason Hsu <jhsu802701@jasonhsu.com>