3.2.3.2 Easy PPP setup with chat

It's far more easey to let the pppd do all the setting of addresses and routes. Furthermore, it can even do the dialing so that you can start up the PPP-connection with a single command.

1. Logging in: All the logging-in is done via a chat-script, that does send the modem the dial-command, and then log into your terminal server, giving it your username and password, and then do the right steps to start the PPP connection. As especially the last step is highly dependent on your provider's terminal/modem-server, no general rules can be told about this here. As an example, I'll use our server who asks for a username ('Username> '), a password ('Password> ') and the offer a menu from where you can choose to start PPP (among other things). One chooses entry #20 from the menu to start PPP on the appropriate prompt ('... use arrow keys:'). With this in mind, put the following in `/etc/ppp/chat':

   ABORT BUSY
   ABORT 'NO CARRIER'
   '' ATZ OK ATD09419431320
   sername>--sername> MYUSERNAME
   assword> MYPASSWORD
   'or use arrow keys:' 20
   

   The first two lines tell chat to abort if the line's busy or there's no carrier. It then dials the modem-server (please change this for yours!), which asks for a username and password, and responds with the appropriate values (please change those two, too!), then asks to choose a item from the menu by either entering the numer or by using the arrow keys. We use item #20 here, and it fires up PPP.
2. Configuring the pppd: In order to let pppd do all the address negotiation, setting of routes etc., you'll have to tell it to do so. You do this by entering the following lines in `/etc/ppp/options':

   crtscts
   defaultroute
   netmask 255.255.255.0
   noipdefault
   ipcp-accept-local
   ipcp-accept-remote
   

   This tells pppd to use RTC/CTS handshaking, set the system's default-route, use the propper netmask and use no default-values for the local and remote IP-numbers but rather to accept them from the remote end's pppd. Please read pppd's manpage, as there are a LOT more options, from which the one or other might be userful for you.
3. Bring up the connection: As you've the chat-script to to automate the login etc., you just start pppd to do the remaining work:

   pppd /dev/tty00 38400 connect "chat -f /etc/ppp/chat"
   

   This will first do the dial-in etc., then use the values given in `/etc/ppp/options' to set the local ip-number, fix the routing tables and make everything go fine. This command can be issued by every user, not only root. After starting up the connection, you can put an optional shell-script in `/etc/ppp/ip-up' that does miscellaneous system initialisations, such as starting a web-proxy, exchange mail, fix your `/etc/resolv.conf', etc.
4. Shutting down the connection: When starting the connection, pppd writes its pid to `/var/run/ppp0.pid'. If you want to end the PPP-session, just kill it:

   kill `cat /var/run/ppp0.pid`
   

   To undo any changes done by the `ip-up' script, you can place another shell-script in `/etc/ppp/ip-down' to e.g. shut down your web proxy, etc.