(copyleft) 2000 by Brian Coyle	brianc@magicnet.net
    	This document may be freely distributed under the FDL.
	http://www.gnu.org/copyleft/fdl.html

UPDATE!  10-17-2000
-------------------

I actually got this implemented!  Details after the ACSII art.



On the ELUG list, while discussing Free ISP options,
Shawn McMahon wrote:
> 
> 
> 2) Get ADSL at home and set up a modem and PPP, dial in to yourself 
> long distance.  :-)
> 

Funny you should mention this...    I was musing over something very
similar today.

I have a 3Com ImpactIQ ISDN modem serial attached to my firewall &
ppp dial-on-demand server.

It occurred to me, I could attach a 56K modem to the 2nd BRI via the
POTS port on the ISDN modem.  Then I could connect the 56K modem
to the server.

This would allow me to setup dial-in access to my local network,
*AND* still be able to connect to my ISP (via the 1st BRI).

Has anyone done anything like this?   Any success stories, URLs, 
or gotchas to pass along?  I'm looking for the pppd / mgetty
specifics - I know about the security issues.

Here's a quick diagram (excuse the ASCII art) to help visualize the
environment:


        ISP      Remote
                 Modem (laptop, etc.)
           \   /
            \ /
             |  Telco ISDN
             |
         ISDN Modem
           |     |
    Serial |     | POTS
    Cable  |     |
           |    56K
           |    Modem
           |       |
           |       |  Serial Cable
           |       |
        +----------------+
        | ttyS0   ttyS1  |    
        |        mgetty  |
        | pppd    pppd   |  Firewall 
        |                |  dial-on-demand 
        |                |  Linux server
        +----------------+ 
               |
               |
               |
    +----+-----+----+-----+    Household LAN
    |    |          |     |
    |    |          |     |
           

Implementation Details--

Following some of the Serial and Modem HOWTOs, I originally setup
uugetty.  This worked when I tested it from home, but I had some
difficulty from ALS2000. This might have been due to some weird 
long distance signalling but in any case, I switched to mgetty.

Super simple-

1) install the mgetty package.

2) create a /usr/local/bin/ppp-login script.  Mine looks like this:


   #!/bin/bash
   # Starts a PPP service for a login
   # From "RH Linux Secrets" page 576

   RMTIP="192.168.1.111"
   LOCIP="192.168.1.222"

   exec /usr/sbin/pppd -detach silent ttyS3 proxyarp crtscts $LOCIP:$RMTIP

3) add a line to /etc/inittab to respawn the mgetty.

   s3:2345:respawn:/sbin/mgetty ttyS3

   ttyS3 is the device your modem is attached to.  Yours may be 
   different.

4) in your /etc/mgetty+sendfax/login.config file change the
   AutoPPP line to run your ppp-login script.

   /AutoPPP/ -	a_ppp	/usr/local/bin/ppp-login

5) create or update your /etc/ppp/pap-secrets file.

   # Secrets for authentication using PAP
   # client	server		secret			IP addresses
   my_username	*		my_passord		*


6) as root, issue 

   # init q

   to have init re-read the /etc/inittab file.

Be sure to review your firewall rules and policies!!

GOOD LUCK!