1 .\" manual page [] for pppd 2.0
2 .\" $Id: pppd.8,v 1.11 1995/05/01 01:46:40 paulus Exp $
4 .\" SS subsection heading
6 .\" IP indented paragraph
10 pppd \- Point to Point Protocol daemon
22 The Point-to-Point Protocol (PPP) provides a method for transmitting
23 datagrams over serial point-to-point links. PPP
24 is composed of three parts: a method for encapsulating datagrams over
25 serial links, an extensible Link Control Protocol (LCP), and
26 a family of Network Control Protocols (NCP) for establishing
27 and configuring different network-layer protocols.
29 The encapsulation scheme is provided by driver code in the kernel.
31 provides the basic LCP, authentication support, and an
32 NCP for establishing and configuring the Internet Protocol (IP)
33 (called the IP Control Protocol, IPCP).
34 .SH FREQUENTLY USED OPTIONS
37 Communicate over the named device. The string "/dev/"
38 is prepended if necessary. If no device name is given,
39 or if the name of the controlling terminal is given,
41 will use the controlling terminal, and will not fork to put itself in
45 Set the baud rate to <speed>. On systems such as 4.4BSD and NetBSD,
46 any speed can be specified. Other systems (e.g. SunOS) allow only a
47 limited set of speeds.
50 Set the async character map to <map>.
51 This map describes which control characters cannot be successfully
52 received over the serial line.
54 will ask the peer to send these characters as a 2-byte escape sequence.
55 The argument is a 32 bit hex number
56 with each bit representing a character to escape.
57 Bit 0 (00000001) represents the character 0x00;
58 bit 31 (80000000) represents the character 0x1f or ^_.
59 If multiple \fBasyncmap\fR options are
60 given, the values are ORed together.
61 If no \fBasyncmap\fR option is given, no async character map will be
62 negotiated for the receive direction; the peer should then escape
63 \fIall\fR control characters.
66 Require the peer to authenticate itself before allowing network
67 packets to be sent or received.
70 Use the executable or shell command specified by \fI<p>\fR to set up the
71 serial line. This script would typically use the "chat" program to
72 dial the modem and start the remote ppp session.
75 Use hardware flow control (i.e. RTS/CTS) to control the flow of data on
79 Disable hardware flow control (i.e. RTS/CTS) on the serial port. If
80 neither the \fBcrtscts\fR nor the \fB\-crtscts\fR option is given,
81 the hardware flow control setting for the serial port is left
85 Use software flow control (i.e. XON/XOFF) to control the flow of data on
86 the serial port. This option is only implemented on Linux systems
90 Add a default route to the system routing tables, using the peer as
91 the gateway, when IPCP negotiation is successfully completed.
92 This entry is removed when the PPP connection is broken.
95 Run the executable or shell command specified by \fI<p>\fR after
96 \fIpppd\fR has terminated the link. This script could, for example,
97 issue commands to the modem to cause it to hang up if hardware modem
98 control signals were not available.
100 .B escape \fIxx,yy,...
101 Specifies that certain characters should be escaped on transmission
102 (regardless of whether the peer requests them to be escaped with its
103 async control character map). The characters to be escaped are
104 specified as a list of hex numbers separated by commas. Note that
105 almost any character can be specified for the \fBescape\fR option,
106 unlike the \fBasyncmap\fR option which only allows control characters
107 to be specified. The characters which may not be escaped are those
108 with hex values 0x20 - 0x3f or 0x5e.
111 Read options from file <f> (the format is described below).
114 Specifies that \fIpppd\fR should use a UUCP-style lock on the serial
115 device to ensure exclusive access to the device.
118 Set the MRU [Maximum Receive Unit] value to <n> for negotiation.
120 will ask the peer to send packets of no more than <n> bytes.
121 The minimum MRU value is 128.
122 The default MRU value is 1500. A value of 296 is recommended for slow
123 links (40 bytes for TCP/IP header + 256 bytes of data).
126 Set the interface netmask to <n>, a 32 bit netmask in "decimal dot" notation
127 (e.g. 255.255.255.0).
130 Enables the "passive" option in the LCP. With this option,
132 will attempt to initiate a connection; if no reply is received from
135 will then just wait passively for a valid LCP packet from the peer
136 (instead of exiting, as it does without this option).
141 will not transmit LCP packets to initiate a connection until a valid
142 LCP packet is received from the peer (as for the `passive' option with
143 old versions of \fIpppd\fR).
146 .I <local_IP_address>\fB:\fI<remote_IP_address>
147 Set the local and/or remote interface IP addresses. Either one may be
148 omitted. The IP addresses can be specified with a host name or in
149 decimal dot notation (e.g. 150.234.56.78). The default local
150 address is the (first) IP address of the system (unless the
152 option is given). The remote address will be obtained from the peer
153 if not specified in any option. Thus, in simple cases, this option is
155 If a local and/or remote IP address is specified with this option,
157 will not accept a different value from the peer in the IPCP
158 negotiation, unless the
161 .B ipcp-accept-remote
162 options are given, respectively.
165 Don't request or allow negotiation of any options for LCP and IPCP (use
169 Disable Address/Control compression negotiation (use default, i.e.
170 address/control field disabled).
173 Disable asyncmap negotiation (use the default asyncmap, i.e. escape
174 all control characters).
181 Increase debugging level (same as the \fBdebug\fR option).
184 Don't fork to become a background process (otherwise
186 will do so if a serial device is specified).
189 Disable IP address negotiation (with this option, the remote IP
190 address must be specified with an option on the command line or in an
194 Disable magic number negotiation. With this option,
196 cannot detect a looped-back line.
199 Disable MRU [Maximum Receive Unit] negotiation (use default, i.e. 1500).
207 Disable protocol field compression negotiation (use default, i.e.
208 protocol field compression disabled).
211 Agree to authenticate using PAP [Password Authentication Protocol] if
212 requested by the peer, and
213 use the data in file <p> for the user and password to send to the
214 peer. The file contains the remote user name, followed by a newline,
215 followed by the remote password, followed by a newline. This option
219 Require the peer to authenticate itself using PAP.
222 Don't agree to authenticate using PAP.
225 Require the peer to authenticate itself using CHAP [Cryptographic
226 Handshake Authentication Protocol] authentication.
229 Don't agree to authenticate using CHAP.
232 Disable negotiation of Van Jacobson style IP header compression (use
233 default, i.e. no compression).
236 Request that the peer compress packets that it sends, using the
237 BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
238 agree to compress packets sent to the peer with a maximum code size of
239 \fInt\fR bits. If \fInt\fR is not specified, it defaults to the value
240 given for \fInr\fR. Values in the range 9 to 15 may be used for
241 \fInr\fR and \fInt\fR; larger values give better compression but
242 consume more kernel memory for compression dictionaries.
243 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
244 compression in the corresponding direction.
247 Disables compression; \fBpppd\fR will not request or agree to compress
248 packets using the BSD-Compress scheme.
251 Increase debugging level (same as \fB\-d\fR).
253 option is given, \fIpppd\fR will log the contents of all control
254 packets sent or received in a readable form. The packets are logged
255 through syslog with facility \fIdaemon\fR and level \fIdebug\fR. This
256 information can be directed to a file by setting up /etc/syslog.conf
257 appropriately (see syslog.conf(5)).
260 Append the domain name <d> to the local host name for authentication
261 purposes. For example, if gethostname() returns the name porsche, but the
262 fully qualified domain name is porsche.Quotron.COM, you would use the
263 domain option to set the domain name to Quotron.COM.
266 Use the modem control lines. This option is the default. With this
269 will wait for the CD (Carrier Detect) signal from the modem to be asserted
270 when opening the serial device
271 (unless a connect script is specified), and it will drop the DTR (Data
272 Terminal Ready) signal briefly when the connection is terminated and before
273 executing the connect script.
274 On Ultrix, this option implies hardware
275 flow control, as for the \fBcrtscts\fR option.
278 Enable debugging code in the kernel-level PPP driver. The argument
279 \fIn\fR is a number which is the sum of the following values: 1 to
280 enable general debug messages, 2 to request that the contents of
281 received packets be printed, and 4 to request that the contents of
282 transmitted packets be printed.
285 Don't use the modem control lines. With this option,
287 will ignore the state of the CD (Carrier Detect) signal from the modem and
288 will not change the state of the DTR (Data Terminal Ready) signal.
291 Set the MTU [Maximum Transmit Unit] value to \fI<n>\fR. Unless the
292 peer requests a smaller value via MRU negotiation, \fIpppd\fR will
293 request that the kernel networking code send data packets of no more
294 than \fIn\fR bytes through the PPP network interface.
297 Set the name of the local system for authentication purposes to <n>.
300 Set the user name to use for authenticating this machine with the peer
304 Enforce the use of the hostname as the name of the local system for
305 authentication purposes (overrides the
310 Set the assumed name of the remote system for authentication purposes
314 Indicates that all secrets in the /etc/ppp/pap-secrets file which
315 are used for checking the identity of the peer are encrypted, and thus
316 pppd should not accept a password which (before encryption) is
317 identical to the secret from the /etc/ppp/pap-secrets file.
320 Add an entry to this system's ARP [Address Resolution Protocol] table
321 with the IP address of the peer and the Ethernet address of this
325 Do not exit after a connection is terminated; instead try to reopen
329 Use the system password database for authenticating the peer using
333 Disables the default behaviour when no local IP address is specified,
334 which is to determine (if possible) the local IP address from the
335 hostname. With this option, the peer will have to supply the local IP
336 address during IPCP negotiation (unless it specified explicitly on the
337 command line or in an options file).
339 .B lcp-echo-interval \fI<n>
340 If this option is given, \fIpppd\fR will send an LCP echo-request
341 frame to the peer every \fIn\fR seconds. Under Linux, the
342 echo-request is sent when no packets have been received from the peer
343 for \fIn\fR seconds. Normally the peer should respond to the
344 echo-request by sending an echo-reply. This option can be used with
345 the \fIlcp-echo-failure\fR option to detect that the peer is no longer
348 .B lcp-echo-failure \fI<n>
349 If this option is given, \fIpppd\fR will presume the peer to be dead
350 if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
351 echo-reply. If this happens, \fIpppd\fR will terminate the
352 connection. Use of this option requires a non-zero value for the
353 \fIlcp-echo-interval\fR parameter. This option can be used to enable
354 \fIpppd\fR to terminate after the physical connection has been broken
355 (e.g., the modem has hung up) in situations where no hardware modem
356 control lines are available.
358 .B lcp-restart \fI<n>
359 Set the LCP restart interval (retransmission timeout) to <n> seconds
362 .B lcp-max-terminate \fI<n>
363 Set the maximum number of LCP terminate-request transmissions to <n>
366 .B lcp-max-configure \fI<n>
367 Set the maximum number of LCP configure-request transmissions to <n>
370 .B lcp-max-failure \fI<n>
371 Set the maximum number of LCP configure-NAKs returned before starting
372 to send configure-Rejects instead to <n> (default 10).
374 .B ipcp-restart \fI<n>
375 Set the IPCP restart interval (retransmission timeout) to <n> seconds
378 .B ipcp-max-terminate \fI<n>
379 Set the maximum number of IPCP terminate-request transmissions to <n>
382 .B ipcp-max-configure \fI<n>
383 Set the maximum number of IPCP configure-request transmissions to <n>
386 .B ipcp-max-failure \fI<n>
387 Set the maximum number of IPCP configure-NAKs returned before starting
388 to send configure-Rejects instead to <n> (default 10).
390 .B pap-restart \fI<n>
391 Set the PAP restart interval (retransmission timeout) to <n> seconds
394 .B pap-max-authreq \fI<n>
395 Set the maximum number of PAP authenticate-request transmissions to
398 .B chap-restart \fI<n>
399 Set the CHAP restart interval (retransmission timeout for challenges)
400 to <n> seconds (default 3).
402 .B chap-max-challenge \fI<n>
403 Set the maximum number of CHAP challenge transmissions to <n> (default
406 .B chap-interval \fI<n>
407 If this option is given,
409 will rechallenge the peer every <n> seconds.
414 will accept the peer's idea of our local IP address, even if the
415 local IP address was specified in an option.
417 .B ipcp-accept-remote
420 will accept the peer's idea of its (remote) IP address, even if the
421 remote IP address was specified in an option.
423 Options can be taken from files as well as the command line.
425 reads options from the files /etc/ppp/options and ~/.ppprc before
426 looking at the command line. An options file is parsed into a series
427 of words, delimited by whitespace. Whitespace can be included in a
428 word by enclosing the word in quotes ("). A backslash (\\) quotes the
429 following character. A hash (#) starts a comment, which continues
430 until the end of the line.
433 provides system administrators with sufficient access control that PPP
434 access to a server machine can be provided to legitimate users without
435 fear of compromising the security of the server or the network it's
436 on. In part this is provided by the /etc/ppp/options file, where the
437 administrator can place options to require authentication whenever
439 is run, and in part by the PAP and CHAP secrets files, where the
440 administrator can restrict the set of IP addresses which individual
443 The default behaviour of
445 is to agree to authenticate if requested, and to not
446 require authentication from the peer. However,
449 authenticate itself with a particular protocol if it has no secrets
450 which could be used to do so.
452 Authentication is based on secrets, which are selected from secrets
453 files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
454 Both secrets files have the same format, and both can store secrets
455 for several combinations of server (authenticating peer) and client
456 (peer being authenticated). Note that
459 and client, and that different protocols can be used in the two
460 directions if desired.
462 A secrets file is parsed into words as for a options file. A secret
463 is specified by a line containing at least 3 words, in the order
464 client name, server name, secret. Any following words on the same line are
465 taken to be a list of acceptable IP addresses for that client. If
466 there are only 3 words on the line, it is assumed that any IP address
467 is OK; to disallow all IP addresses, use "-". If the secret starts
468 with an `@', what follows is assumed to be the name of a file from
469 which to read the secret. A "*" as the client or server name matches
470 any name. When selecting a secret, \fIpppd\fR takes the best match, i.e.
471 the match with the fewest wildcards.
473 Thus a secrets file contains both secrets for use in authenticating
474 other hosts, plus secrets which we use for authenticating ourselves to
475 others. Which secret to use is chosen based on the names of the host
476 (the `local name') and its peer (the `remote name'). The local name
479 if the \fBusehostname\fR option is given,
480 then the local name is the hostname of this machine
481 (with the domain appended, if given)
483 else if the \fBname\fR option is given,
484 then use the argument of the first \fBname\fR option seen
486 else if the local IP address is specified with a hostname,
489 else use the hostname of this machine (with the domain appended, if given)
491 When authenticating ourselves using PAP, there is also a `username'
492 which is the local name by default, but can be set with the \fBuser\fR
493 option or the \fB+ua\fR option.
495 The remote name is set as follows:
497 if the \fBremotename\fR option is given,
498 then use the argument of the last \fBremotename\fR option seen
500 else if the remote IP address is specified with a hostname,
501 then use that host name
503 else the remote name is the null string "".
505 Secrets are selected from the PAP secrets file as follows:
508 For authenticating the peer, look for a secret with client ==
509 username specified in the PAP authenticate-request, and server ==
513 For authenticating ourselves to the peer, look for a secret with
514 client == our username, server == remote name.
516 When authenticating the peer with PAP, a secret of "" matches any
517 password supplied by the peer. If the password doesn't match the
518 secret, the password is encrypted using crypt() and checked against
519 the secret again; thus secrets for authenticating the peer can be
520 stored in encrypted form. If the \fBpapcrypt\fR option is given, the
521 first (unencrypted) comparison is omitted, for better security.
523 If the \fBlogin\fR option was specified, the
524 username and password are also checked against the system password
525 database. Thus, the system administrator can set up the pap-secrets
526 file to allow PPP access only to certain users, and to restrict the
527 set of IP addresses that each user can use. Typically, when using the
528 \fBlogin\fR option, the secret in /etc/ppp/pap-secrets would be "", to
529 avoid the need to have the same secret in two places.
531 Secrets are selected from the CHAP secrets file as follows:
534 For authenticating the peer, look for a secret with client == name
535 specified in the CHAP-Response message, and server == local name.
538 For authenticating ourselves to the peer, look for a secret with
539 client == local name, and server == name specified in the
540 CHAP-Challenge message.
542 Authentication must be satisfactorily completed before IPCP (or any
543 other Network Control Protocol) can be started. If authentication
544 fails, \fIpppd\fR will terminated the link (by closing LCP). If IPCP
545 negotiates an unacceptable IP address for the remote host, IPCP will
546 be closed. IP packets can only be sent or received when IPCP is open.
548 In some cases it is desirable to allow some hosts which can't
549 authenticate themselves to connect and use one of a restricted set of
550 IP addresses, even when the local host generally requires
551 authentication. If the peer refuses to authenticate itself when
552 requested, \fIpppd\fR takes that as equivalent to authenticating with
553 PAP using the empty string for the username and password. Thus, by
554 adding a line to the pap-secrets file which specifies the empty string
555 for the client and password, it is possible to allow restricted access
556 to hosts which refuse to authenticate themselves.
559 When IPCP negotiation is completed successfully,
561 will inform the kernel of the local and remote IP addresses for the
562 ppp interface. This is sufficient to create a
563 host route to the remote end of the link, which will enable the peers
564 to exchange IP packets. Communication with other machines generally
565 requires further modification to routing tables and/or ARP (Address
566 Resolution Protocol) tables. In some cases this will be done
567 automatically through the actions of the \fIrouted\fR or \fIgated\fR
568 daemons, but in most cases some further intervention is required.
570 Sometimes it is desirable
571 to add a default route through the remote host, as in the case of a
572 machine whose only connection to the Internet is through the ppp
573 interface. The \fBdefaultroute\fR option causes \fIpppd\fR to create such a
574 default route when IPCP comes up, and delete it when the link is
577 In some cases it is desirable to use proxy ARP, for example on a
578 server machine connected to a LAN, in order to allow other hosts to
579 communicate with the remote host. The \fBproxyarp\fR option causes \fIpppd\fR
580 to look for a network interface on the same subnet as the remote host
581 (an interface supporting broadcast and ARP, which is up and not a
582 point-to-point or loopback interface). If found, \fIpppd\fR creates a
583 permanent, published ARP entry with the IP address of the remote host
584 and the hardware address of the network interface found.
587 In the simplest case, you can connect the serial ports of two machines
588 and issue a command like
590 pppd /dev/ttya 9600 passive
592 to each machine, assuming there is no \fIgetty\fR running on the
593 serial ports. If one machine has a \fIgetty\fR running, you can use
594 \fIkermit\fR or \fItip\fR on the other machine to log in to the first
595 machine and issue a command like
599 Then exit from the communications program (making sure the connection
600 isn't dropped), and issue a command like
604 The process of logging in to the other machine and starting \fIpppd\fR
605 can be automated by using the \fBconnect\fR option to run \fIchat\fR,
608 pppd /dev/ttya 38400 connect 'chat "" "" "login:" "username"
609 "Password:" "password" "% " "exec pppd passive"'
611 (Note however that running chat like this will leave the password
612 visible in the parameter list of pppd and chat.)
614 If your serial connection is any more complicated than a piece of
615 wire, you may need to arrange for some control characters to be
616 escaped. In particular, it is often useful to escape XON (^Q) and
617 XOFF (^S), using \fBasyncmap a0000\fR. If the path includes a telnet,
618 you probably should escape ^] as well (\fBasyncmap 200a0000\fR).
619 If the path includes an rlogin, you will need to use the \fBescape
620 ff\fR option on the end which is running the rlogin client, since many
621 rlogin implementations are not
622 transparent; they will remove the sequence [0xff, 0xff, 0x73, 0x73,
623 followed by any 8 bytes] from the stream.
626 Messages are sent to the syslog daemon using facility LOG_DAEMON.
627 (This can be overriden by recompiling \fIpppd\fR with the macro
628 LOG_PPP defined as the desired facility.) In order to see the error
629 and debug messages, you will need to edit your /etc/syslog.conf file
630 to direct the messages to the desired output device or file.
632 The \fBdebug\fR option causes the contents of all control packets sent
633 or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
634 This can be useful if the PPP negotiation does not succeed.
635 If debugging is enabled at compile time, the \fBdebug\fR option also
636 causes other debugging messages to be logged.
638 Debugging can also be enabled or disabled by sending a
641 process. This signal acts as a toggle.
644 .B /var/run/ppp\fIn\fB.pid \fR(BSD or Linux), \fB/etc/ppp/ppp\fIn\fB.pid \fR(others)
645 Process-ID for \fIpppd\fR process on ppp interface unit \fIn\fR.
648 A program or script which is executed when the link is available for
649 sending and receiving IP packets (that is, IPCP has come up). It is
650 executed with the parameters
652 \fIinterface-name tty-device speed local-IP-address
655 and with its standard input,
656 output and error streams redirected to \fB/dev/null\fR.
658 This program or script is executed with the same real and effective
659 user-ID as \fIpppd\fR, that is, at least the effective user-ID and
660 possibly the real user-ID will be \fBroot\fR. This is so that it can
661 be used to manipulate routes, run privileged daemons (e.g.
662 \fBsendmail\fR), etc. Be careful that the contents of the
663 /etc/ppp/ip-up and /etc/ppp/ip-down scripts do not compromise your
667 A program or script which is executed when the link is no longer
668 available for sending and receiving IP packets. This script can be
669 used for undoing the effects of the /etc/ppp/ip-up script. It is
670 invoked with the same parameters as the ip-up script, and the same
671 security considerations apply, since it is executed with the same
672 effective and real user-IDs as \fIpppd\fR.
674 .B /etc/ppp/pap-secrets
675 Usernames, passwords and IP addresses for PAP authentication.
677 .B /etc/ppp/chap-secrets
678 Names, secrets and IP addresses for CHAP authentication.
681 System default options for
683 read before user default options or command-line options.
686 User default options, read before command-line options.
688 .B /etc/ppp/options.\fIttyname
689 System default options for the serial port being used, read after
690 command-line options.
695 .I Compressing TCP/IP headers for low-speed serial links.
700 .I The MD5 Message-Digest Algorithm.
705 .I PPP Internet Protocol Control Protocol (IPCP).
709 Lloyd, B.; Simpson, W.A.
710 .I PPP authentication protocols.
715 .I The Point\-to\-Point Protocol (PPP).
720 .I PPP in HDLC Framing.
723 The following signals have the specified effect when sent to the
728 These signals cause \fBpppd\fR to terminate the link (by closing LCP),
729 restore the serial device settings, and exit.
732 This signal causes \fBpppd\fR to terminate the link, restore the
733 serial device settings, and close the serial device. If the
734 \fBpersist\fR option has been specified, \fBpppd\fR will try to reopen
735 the serial device and start another connection. Otherwise \fBpppd\fR
741 to renegotiate compression. This can be useful to re-enable
742 compression after it has been disabled as a result of a fatal
743 decompression error. With the BSD Compress scheme, fatal
744 decompression errors generally indicate a bug in one or other
753 Paul Mackerras (paulus@cs.anu.edu.au).
projects / ppp.git / blob