Author
Christopher Marshall (christopherlmarshall@yahoo.com)
Raw Notes on PPP
# common speeds
19200
38400
57600
115200
# experiments
# nodetach helps with testing by not detaching the pppd process from the controlling
# terminal, allowing you to cntl-c to kill it when something goes wrong, and also
# causing error messages to be printed to stdout instead of just to the syslog.
# local means "don't use modem control lines"
# pty lets you specify an arbitrary command to run to receive packets from
# which is great for VPN's
# general advice: remove /etc/ppp/options before trying experiments because you never
# know what other options you might be relying on that are in /etc/ppp/options unless
# you zero them out first.
# pty/tty pair
pppd /dev/ptyp0 nodetach local 10.5.0.1:10.5.0.2
pppd /dev/ttyp0 nodetach local
# using pty argument
pppd nodetach pty "pppd notty 10.0.3.1:10.0.3.2"
pppd nodetach 10.0.3.1:10.0.3.2 pty "pppd notty"
# ssh/ppp VPN
pppd nodetach 10.1.0.2:10.1.0.1 pty "ssh -l root remotehost pppd notty"
# how to check the speed of the serial port once pppd takes it over
stty -F /dev/ttyS0
# important files
options in /etc/ppp/options
# procedure for hooking up two machines, A and B
# on A
pppd /dev/ttyS0 115200 crtscts 10.3.0.1:10.3.0.2
# on B
pppd /dev/ttyS0 115200 crtscts
# from within a minicom login-prompt of A to B
minicom
login
su
pppd 115200 crtscts
cntl-AZ from minicom
pppd /dev/ttyS0 115200 crtscts 10.3.0.1:10.3.0.2
# for a dial-in server (this is clever!). This is even easier than
# getting mgetty to work.
pppd /dev/ttyS0 115200 modem crtscts init "chat '' ATZ OK ATS0=1 OK"
# another route
adduser dialin
edit shell in /etc/passwd for user dialin from /bin/bash to /usr/sbin/pppd
remove home directory for security reasons
chmod u+s /usr/sbin/pppd
edit /etc/ppp/options
115200
10.3.0.1:10.3.0.2
minicom from another host
log in as user dialin
cntl-AQ from minicom
pppd /dev/ttyS0 115200 crtscts
you're in!
# two modems are connected and you want to bring up a ppp link
# I illustrate the procedure for directly connected modems (long haul cable)
# I was setting the speed too low which prevented this from working
# Would this work if I didn't set a speed? What does pppd do with the speed?
# "nodetach debug" are life savers!
# If you don't assign IP addresses or some other protocol, like IPX, the link fails.
# Why can't I talk to a modem by echoing commands to /dev/ttyS0?
A:
minicom; atm0; atx3; atd; cntl-A-Q
stty -F /dev/ttyS0
38400 baud
pppd /dev/ttyS0 38400 nodetach debug 10.3.0.1:10.3.0.2
B:
minicom; atm0; atx3; ata; cntl-A-Q
stty -F /dev/ttyS0
38400 baud
pppd /dev/ttyS0 38400 nodetach debug