If you would like to setup your network to automatically dial up the Internet,
either the Diald demand dial-up or new
versions of the PPPd packages will be of
great utility. Diald is the recommended solution due to its more granular
configuration.
Once Diald and IP Masq have been setup properly, any MASQed client machines
that initiate a web, telnet or ftp session will make the Linux box dynamically
bring up its Internet link.
There is a timeout that will occur with the first connection. This is
inevitable if you are using analog modems. The time taken to establish the
modem link and the PPP connections may cause your client program (WWW browser,
etc.) to stop. This isn't common though. If this does happen, just retry that
Internet traffic request (say a WWW page) again and it should come up fine. You
can also try setting
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
kernel option to help with this initial setup.