ppp_manual_setup(7)ppp_manual_setup(7)NAMEppp_manual_setup - Describes how to manually set up Point-to-Point Pro‐
tocol (PPP) connections
DESCRIPTION
The Point-to-Point Protocol (PPP) provides a standard way to transmit
IP datagrams over a serial link and a standard way for the systems
(peers) at either end of the link to negotiate various optional charac‐
teristics of the link. Using PPP, a serial link can be used to trans‐
mit Internet Protocol (IP) datagrams, allowing TCP/IP connections
between the peers.
Note that although you do not use a network interface with PPP, you
must have a network interface configured on your system for the network
daemons (such as nfsd and rwhod) to run properly. The network inter‐
face must be configured with a new IPv4 address. For example, if you
have a personal computer that you use at home and in the office, do not
use the same IPv4 address for the network interface at home as you use
in the office.
MANAGING ROUTING
You can use the gated daemon to manage IPv4 routing and the ip6rtrd
daemon to manage IPv6 routing, if you are not using the PPP connection
solely to communicate between the two systems making the connection.
If you plan to use a system as an IP router, it must be configured to
allow the forwarding of IP packets. For more information on setting a
system up as an IP router, see the Network Administration: Connections
manual and iprsetup(8).
PPP PHYSICAL CONNECTIONS
You can connect systems either directly to each other (using a null
modem), if they are in close proximity, or over telephone lines using
modems, if they are not.
If you connect the systems directly, use a null modem cable, such as
BC22D-xx (where xx varies depending on the length of the cable) to con‐
nect the serial ports on the two hosts. The maximum length of this
type of connection is defined by the RS-232 standard.
If the systems are not in close proximity to each other, you can con‐
nect them using telephone line and modems. To use this kind of connec‐
tion, attach a modem to a serial port on both hosts so that the two
hosts can establish a serial connection between them. You can use an
RS-232 cable connected to the serial port on the host. This cable must
be a straight-through cable such as BC22E-xx or BC22F-xx and the modems
must be set to 8 bit, no parity.
MODEMS
PPP works best when hardware flow control is used. High speed modems
often fall-back to a lower data rate when line degradation occurs. To
support hardware flow control you must use cables with a sufficient
number of wires for full modem control. DECconnect cables do not pro‐
vide a sufficient number of wires. Therefore, do not use them. See
modem(7) for a list of modem cables to use and modem guidelines.
Note
Do not use XON/XOFF flow control. It will corrupt the data stream
causing the TCP layer over IP to issue retransmit requests for over-
runs.
AUTHENTICATION
PPP provides three protocols for authenticating hosts and for authenti‐
cating your host system to others: Password Authentication Protocol
(PAP) Challenge Handshake Authentication Protocol (CHAP) Microsoft
Challenge Handshake Authentication Protocol (MS-CHAP)
All protocols exchange secrets in order to complete the authentication
process. PAP secrets are contained in the /etc/ppp/pap-secrets file;
CHAP secrets are contained in the /etc/ppp/chap-secrets file. Only
root should be able to read these files.
The pap-secrets and chap-secrets files should have the following for‐
mat: client server secret ip_address...
Name of the machine being authenticated. Name of the machine requiring
authentication. Password or CHAP secret known by both client and
server. Zero or more IPv4 addresses that the client may use (this
field is used only on the server).
The MS-CHAP protocol exchange secrets are located in the /etc/ppp/chap-
secrets file. The format for this protocol is as follows: username
server secret
Name of the user to be authenticated. Name of the machine requiring
authentication. Password or CHAP secret known by both client and
server.
Note
The /etc/ppp directory contains files of secrets used for
authentication, and should not be in a partition that is
exported using NFS and accessible to other hosts.
If authentication is required, the /etc/ppp/options file must
contain the auth and usehostname options.
VERIFYING PPP SUPPORT IN THE KERNEL
Verify that PPP is supported in the kernel by entering the following
command: # sysconfig -s | grep ppp
If it is not loaded and configured, do the following: Log in as root.
Rebuild the kernel by running the doconfig program and selecting the
Point-to-Point (PPP) option. Make a backup copy of the current /vmunix
file. Copy the newly-created /sys/HOSTNAME/vmunix kernel file to the
/vmunix file. Reboot the system
PPP CONNECTIONS
A PPP connection between two systems involves setting up a serial link
and running the PPP daemon, pppd, on both ends of the link. Guidelines
for running pppd are as follows: If you want to run IPv6 over PPP, set
the Maximum Receive Unit (mru) parameter to 1280 or higher. See
pppd(8) for more information. If you want the interface ID for IPv6
over PPP to differ from the address for the local host's Ethernet or
other broadcast interface, put the desired address on the pppd command
line with a colon appended as follows:
ip6cp-interface-id interface-id: If you want the local address
of the PPP link to differ from the IPv4 address for the local
host's Ethernet or other broadcast interface, put the desired
address on the pppd command line with a colon appended as fol‐
lows:
local_addr: Do not use ifconfig to configure the addresses of
the PPP interface. The pppd daemon assigns addresses and iden‐
tifies the interface as active. Whether you run pppd manually
on the remote machine or use a script file on the local machine
to run pppd on the remote machine, do not provide a device name
to pppd; it uses the controlling tty by default.
For information on pppd options, see pppd(8) and Network Administra‐
tion: Connections.
ESTABLISHING A PPP DIAL-OUT CONNECTION
To a PPP dial-out connection, do the following: Verify that you can
communicate with the modem. Do the following: Edit the /etc/remote
file and copy the kdebug entry. Modify the new entry, providing a sys‐
tem name for the entry, the correct Tru64 UNIX device (tty00 or tty01
depending on your system), the correct baud rate, and correct parity.
See remote(4) for more information. Check the /usr/spool/locks direc‐
tory for LCK..ttynn lock files. If any exist for the terminal device
you are configuring for PPP, remove them.
When you establish a connection over a terminal device, the sys‐
tem generates a lock file to prevent the connection from being
disrupted by another application. If the connection terminates
abnormally, the lock file might persist, preventing you from
establishing new connections. Use the tip command to access the
modem as follows: % tip system_name
system_name is the system name from the /etc/remote file.
Note
Be sure you do not have a getty process running on the port to
which the modem is connected.
For more information on the tip command, see tip(1) and the Com‐
mand and Shell User's Guide. If your modem is using the AT com‐
mand language, enter the following command: AT <Return>
If the modem is not in quiet mode, it responds with an OK mes‐
sage. Contact the remote system administrator or your Internet
Service Provider (ISP) and obtain the following information:
Your remote IPv4 address and netmask, unless the remote system
assigns the IPv4 address dynamically (IPv4 over PPP only) Char‐
acters that might need to be escaped Instructions on how to log
in and use the remote service
This information is used to create a chat script, which auto‐
mates the dial-out process. Create a file for commands that the
chat program uses to direct the modem what number to dial and
what to send the remote system in order to start pppd. This
file is called a chat script. Each entry in a chat script has
the following format:
string_chat_expects string_chat_sends
See chat(8) for more information onchat and chat scripts. Copy
the PPP options file template from the /etc/ppp.common directory
to the /etc/ppp directory, as follows: # cp /etc/ppp.com‐
mon/options /etc/ppp
This file must exist and must be readable by pppd; otherwise,
the daemon will not run. Set the file permissions so that only
root has write access: # ls -l /etc/ppp/options -rw-r--r-- 1
root bin 3348 Feb 26 22:32 options Edit the
/etc/ppp/options file and include the pppd options as required
by the remote system or ISP. See pppd(8) for a complete list of
pppd options. See Network Administration: Connections for a
sample /etc/ppp/options file for dial-out access. Edit the
/etc/syslog.conf file and do the following to enable logging for
PPP: Add the local2 facility (used by pppd and chat) to the line
that specifies /dev/console as the message destination as fol‐
lows:
kern.debug;local2.notice /dev/console
In this example, the notice level is specified. Add the follow‐
ing entry to the file to create a ppp-log file:
local2.debug /etc/ppp/ppp-log Save the edits
and close the file.
See syslogd(8) for more information. Create the ppp-log file by
issuing the following command: # touch /etc/ppp/ppp-log
This file must be created before the next step to ensure that
PPP event logging is started. Stop and start syslogd by enter‐
ing the following commands: # /sbin/init.d/syslog stop #
/sbin/init.d/syslog start Invoke pppd on the local system to
connect to the remote system. For example, the following command
starts a link on tty01 and specifies the connect option to run
the chat program using the specified chat script file. % pppd
/dev/tty01 38400 connect \ 'chat -v -f /etc/ppp/chat-script'
Issue the following command to monitor the ppp-log file and
determine whether the PPP connection is active: % tail -f
/etc/ppp/ppp-log
After you have established a connection, you can use the pppstats and
netstat commands to obtain current statistics for the PPP interface.
For example: % pppstats
IN PACK VJCOMP VJUNC VJERR | OUT PACK VJCOMP VJUNC NON-VJ
9425 311 5 2 0 | 9574 308 1 3 304
% netstat -I ppp0
Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll
ppp0 1500 <Link> Link#6 305 0 302 0 0
ppp0 1500 10 10.1.2.2 305 0 302 0 0
For more information about the pppstats and netstat commands, see ppp‐
stats(8) and netstat(1).
If any problems occur while using PPP, see the Network Administration:
Connections manual.
ESTABLISHING A DIAL-IN CONNECTION
To configure a PPP dial-in system, complete the following steps: Set up
your modem for dial-in accss. See modem(7) for more information. Edit
the /etc/passwd file and create a dedicated entry for a PPP user. For
the login shell field, specify /usr/sbin/startppp; for example:
ppp1:password:10:20:Remote PPP
User:/usr/users/guest:/usr/sbin/startppp Edit the /etc/inittab
file and create an entry for each terminal device that is to run
PPP. For example:
modem:3:respawn:/usr/sbin/getty /dev/tty00 M38400 vt100
See inittab(4) for more information. Issue the init q command
to start the getty process immediately. If the dial-in system
is going to be a gateway for the dial-out system to reach other
systems on the LAN, the dial-in system must be configured as an
IP router and must also run one of the following daemons: For
IPv4 routing, run the gated daemon. Edit the /etc/gated.conf
file and delete the nobroadcast option (if specified) in the rip
statement. See the Network Administration: Connections manual
for basic network setup information and gated.conf(4) for gated
options. For IPv6 routing, run the ip6rtrd daemon. You must
include the ppp interface in the ip6rtrd.conf file. See
ip6_setup(8) for more information. In addition, set the
ipv6forwarding and ip6gateway kernel configuration attributes to
1. Copy the PPP options file template from the /etc/ppp.common
directory to the /etc/ppp directory, as follows: # cp
/etc/ppp.common/options /etc/ppp
This file must exist and must be readable by pppd; otherwise,
the daemon will not run. Set the file permissions so that only
root has write access: # ls -l /etc/ppp/options -rw-r--r-- 1
root bin 3348 Feb 26 22:32 options Edit the
/etc/ppp/options file and include the pppd options required to
support dial-in access for all remote users. See Network Admin‐
istration: Connections for a sample /etc/ppp/options file for
dial-in access.
If you want to specify options for each individual serial port,
create a /etc/ppp/options.ttyxx file and include the remote IP
address and any other options that apply to that specific serial
port. See pppd(8) for a complete list ofpppd options. After an
incoming call is received and a connection established, startppp
runs in the background. The process ID is logged in the
/etc/ppp/pppxx.pid file.
If any problems occur while using PPP, see the Network Administration:
Connections manual.
TERMINATING PPP CONNECTIONS
To terminate the PPP link, send a TERM or INTR signal to one of the
pppd daemons by issuing the following command: # kill `cat
/etc/ppp/pppxx.pid`
In this command, pppxx specifies the pppd used for the PPP connection.
The pppd specified in the command also instructs other pppd daemons to
terminate.
If pppd is attached to a hardware serial port that is connected to a
modem, the daemon should get a HUP signal when the modem hangs up,
which will cause it to clean up and exit. This action depends on the
driver and its current settings.
Do not use a SIGKILL (kill -9) to terminate the process. It might not
allow the pppd daemon to terminate properly, which could corrupt the
tty files.
SEE ALSO
Files: gated.conf(4), inittab(4), ip6rtrd.conf(4), remote(4)
Daemons: ip6rtrd(8), nd6hostd(8), pppd(8), syslogd(8)
Commands: tip(1), chat(8), iprsetup(8), netstat(1), pppd(8), ppp‐
stats(8), syslogd(8)
Networks: modem(7)
Network Administration: Connections
RFC 1332, The PPP Internet Protocol Control Protocol (IPCP), G. McGre‐
gor
RFC 1334, PPP Authentication Protocols, B. Lloyd, W. Simpson
RFC 1661, The Point-to-Point Protocol (PPP), W. Simpson
RFC 1662, PPP in HDLC-like Framing, W. Simpson
RFC 2461, Neighbor Discovery for IP Version 6 (IPv6), T. Narten, E.
Nordmark, and W. A. Simpson
RFC 2472, IP Version 6 over PPP
ppp_manual_setup(7)
