Need help w/routing between Eth0 and modem

[Scott Ehrlich <scott@ehrlichtronics.com>]

I have a Compaq Armada M700 laptop with a built-in Intel Pro 100+ miniPCI
NIC and a built-in Lucent LT WinModem modem.  I want to configure the
system as a personal ISP such that I can dial into the machine from my PDA
and cell phone and have it route calls to my Linksys "Broadband"
router/hub (befsr81) which then connects to my cable modem.  If the Lucent
WinModem is impossible or too much of a pain, I have a genuine USR
Sportster external 14.4k modem I can plug into the serial port, but I to
try with the WinModem, first.

I want to configure the modem to only accept an incoming _data_ call from
my cell phone then issue a dynamic IP address, and then work with the NIC
for the rest.  If anyone else calls, or if I establish a voice call from
my cell phone, I want the modem to ignore the incoming call.   Also, how
do I handle/configure user authentication for dial-in access?   Would it
be part of the PPP config?    How is the dial-in DHCP pool defined?

I am not knew to linux or debian or networking, but I've never set up this
kind of configuration before and would really appreciate help and
guidance.   I am planning to use the recent Debian testing for my
install, unless people suggest otherwise.

I also look to take advantage of the ability to remote control/fix things
via an ssh client on my PDA (tussh) if something went wrong or needed to
be changed.

Thank you.

Scott