1 .\" manual page [] for pppd 2.0
2 .\" $Id: pppd.8,v 1.8 1994/09/16 02:32:09 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,
40 will use the controlling terminal, and will not fork to put itself in
44 Set the baud rate to <speed>. On systems such as 4.4BSD and NetBSD,
45 any speed can be specified. Other systems (e.g. SunOS) allow only a
46 limited set of speeds.
49 Set the async character map to <map>.
50 This map describes which control characters cannot be successfully
51 received over the serial line.
53 will ask the peer to send these characters as a 2-byte escape sequence.
54 The argument is a 32 bit hex number
55 with each bit representing a character to escape.
56 Bit 0 (00000001) represents the character 0x00;
57 bit 31 (80000000) represents the character 0x1f or ^_.
58 If multiple \fBasyncmap\fR options are
59 given, the values are ORed together.
60 If no \fBasyncmap\fR option is given, no async character map will be
61 negotiated for the receive direction; the peer should then escape
62 \fIall\fR control characters.
65 Require the peer to authenticate itself before allowing network
66 packets to be sent or received.
69 Use the executable or shell command specified by \fI<p>\fR to set up the
70 serial line. This script would typically use the "chat" program to
71 dial the modem and start the remote ppp session.
74 Use hardware flow control (i.e. RTS/CTS) to control the flow of data on
78 Disable hardware flow control (i.e. RTS/CTS) on the serial port. If
79 neither the \fBcrtscts\fR nor the \fB\-crtscts\fR option is given,
80 the hardware flow control setting for the serial port is left
84 Use software flow control (i.e. XON/XOFF) to control the flow of data on
85 the serial port. This option is only implemented on Linux systems
89 Add a default route to the system routing tables, using the peer as
90 the gateway, when IPCP negotiation is successfully completed.
91 This entry is removed when the PPP connection is broken.
94 Run the executable or shell command specified by \fI<p>\fR after
95 \fIpppd\fR has terminated the link. This script could, for example,
96 issue commands to the modem to cause it to hang up if hardware modem
97 control signals were not available.
99 .B escape \fIxx,yy,...
100 Specifies that certain characters should be escaped on transmission
101 (regardless of whether the peer requests them to be escaped with its
102 async control character map). The characters to be escaped are
103 specified as a list of hex numbers separated by commas. Note that
104 almost any character can be specified for the \fBescape\fR option,
105 unlike the \fBasyncmap\fR option which only allows control characters
106 to be specified. The characters which may not be escaped are those
107 with hex values 0x20 - 0x3f or 0x5e.
110 Read options from file <f> (the format is described below).
113 Specifies that \fIpppd\fR should use a UUCP-style lock on the serial
114 device to ensure exclusive access to the device.
117 Set the MRU [Maximum Receive Unit] value to <n> for negotiation.
119 will ask the peer to send packets of no more than <n> bytes.
120 The minimum MRU value is 128.
121 The default MRU value is 1500. A value of 296 is recommended for slow
122 links (40 bytes for TCP/IP header + 256 bytes of data).
125 Set the interface netmask to <n>, a 32 bit netmask in "decimal dot" notation
126 (e.g. 255.255.255.0).
129 Enables the "passive" option in the LCP. With this option,
131 will attempt to initiate a connection; if no reply is received from
134 will then just wait passively for a valid LCP packet from the peer
135 (instead of exiting, as it does without this option).
140 will not transmit LCP packets to initiate a connection until a valid
141 LCP packet is received from the peer (as for the `passive' option with
142 old versions of \fIpppd\fR).
145 .I <local_IP_address>\fB:\fI<remote_IP_address>
146 Set the local and/or remote interface IP addresses. Either one may be
147 omitted. The IP addresses can be specified with a host name or in
148 decimal dot notation (e.g. 150.234.56.78). The default local
149 address is the (first) IP address of the system (unless the
151 option is given). The remote address will be obtained from the peer
152 if not specified in any option. Thus, in simple cases, this option is
154 If a local and/or remote IP address is specified with this option,
156 will not accept a different value from the peer in the IPCP
157 negotiation, unless the
160 .B ipcp-accept-remote
161 options are given, respectively.
164 Don't request or allow negotiation of any options for LCP and IPCP (use
168 Disable Address/Control compression negotiation (use default, i.e.
169 address/control field disabled).
172 Disable asyncmap negotiation (use the default asyncmap, i.e. escape
173 all control characters).
180 Increase debugging level (same as the \fBdebug\fR option).
183 Don't fork to become a background process (otherwise
185 will do so if a serial device is specified).
188 Disable IP address negotiation (with this option, the remote IP
189 address must be specified with an option on the command line or in an
193 Disable magic number negotiation. With this option,
195 cannot detect a looped-back line.
198 Disable MRU [Maximum Receive Unit] negotiation (use default, i.e. 1500).
206 Disable protocol field compression negotiation (use default, i.e.
207 protocol field compression disabled).
210 Agree to authenticate using PAP [Password Authentication Protocol] if
211 requested by the peer, and
212 use the data in file <p> for the user and password to send to the
213 peer. The file contains the remote user name, followed by a newline,
214 followed by the remote password, followed by a newline. This option
218 Require the peer to authenticate itself using PAP.
221 Don't agree to authenticate using PAP.
224 Require the peer to authenticate itself using CHAP [Cryptographic
225 Handshake Authentication Protocol] authentication.
228 Don't agree to authenticate using CHAP.
231 Disable negotiation of Van Jacobson style IP header compression (use
232 default, i.e. no compression).
235 Request that the peer compress packets that it sends, using the
236 BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
237 agree to compress packets sent to the peer with a maximum code size of
238 \fInt\fR bits. If \fInt\fR is not specified, it defaults to the value
239 given for \fInr\fR. Values in the range 9 to 15 may be used for
240 \fInr\fR and \fInt\fR; larger values give better compression but
241 consume more kernel memory for compression dictionaries.
242 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
243 compression in the corresponding direction.
246 Disables compression; \fBpppd\fR will not request or agree to compress
247 packets using the BSD-Compress scheme.
250 Increase debugging level (same as \fB\-d\fR).
252 option is given, \fIpppd\fR will log the contents of all control
253 packets sent or received in a readable form. The packets are logged
254 through syslog with facility \fIdaemon\fR and level \fIdebug\fR. This
255 information can be directed to a file by setting up /etc/syslog.conf
256 appropriately (see syslog.conf(5)).
259 Append the domain name <d> to the local host name for authentication
260 purposes. For example, if gethostname() returns the name porsche, but the
261 fully qualified domain name is porsche.Quotron.COM, you would use the
262 domain option to set the domain name to Quotron.COM.
265 Use the modem control lines. This option is the default. With this
268 will wait for the carrier detect signal from the modem to be asserted
269 when opening the serial device
270 (unless a connect script is specified), and it will drop the data
271 terminal ready signal briefly when the connection is terminated and before
272 executing the connect script.
273 On Ultrix, this option implies hardware
274 flow control, as for the \fBcrtscts\fR option.
277 Enable debugging code in the kernel-level PPP driver. The argument
278 \fIn\fR is a number which is the sum of the following values: 1 to
279 enable general debug messages, 2 to request that the contents of
280 received packets be printed, and 4 to request that the contents of
281 transmitted packets be printed.
284 Don't use the modem control lines. With this option,
286 will ignore the state of the carrier detect signal from the modem and
287 will not change the state of the data terminal ready signal.
290 Set the MTU [Maximum Transmit Unit] value to \fI<n>\fR. Unless the
291 peer requests a smaller value via MRU negotiation, \fIpppd\fR will
292 request that the kernel networking code send data packets of no more
293 than \fIn\fR bytes through the PPP network interface.
296 Set the name of the local system for authentication purposes to <n>.
299 Set the user name to use for authenticating this machine with the peer
303 Enforce the use of the hostname as the name of the local system for
304 authentication purposes (overrides the
309 Set the assumed name of the remote system for authentication purposes
313 Add an entry to this system's ARP [Address Resolution Protocol] table
314 with the IP address of the peer and the Ethernet address of this
318 Do not exit after a connection is terminated; instead try to reopen
322 Use the system password database for authenticating the peer using
326 Disables the default behaviour when no local IP address is specified,
327 which is to determine (if possible) the local IP address from the
328 hostname. With this option, the peer will have to supply the local IP
329 address during IPCP negotiation (unless it specified explicitly on the
330 command line or in an options file).
332 .B lcp-echo-interval \fI<n>
333 If this option is given, \fIpppd\fR will send an LCP echo-request
334 frame to the peer every \fIn\fR seconds. Under Linux, the
335 echo-request is sent when no packets have been received from the peer
336 for \fIn\fR seconds. Normally the peer should respond to the
337 echo-request by sending an echo-reply. This option can be used with
338 the \fIlcp-echo-failure\fR option to detect that the peer is no longer
341 .B lcp-echo-failure \fI<n>
342 If this option is given, \fIpppd\fR will presume the peer to be dead
343 if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
344 echo-reply. If this happens, \fIpppd\fR will terminate the
345 connection. Use of this option requires a non-zero value for the
346 \fIlcp-echo-interval\fR parameter. This option can be used to enable
347 \fIpppd\fR to terminate after the physical connection has been broken
348 (e.g., the modem has hung up) in situations where no hardware modem
349 control lines are available.
351 .B lcp-restart \fI<n>
352 Set the LCP restart interval (retransmission timeout) to <n> seconds
355 .B lcp-max-terminate \fI<n>
356 Set the maximum number of LCP terminate-request transmissions to <n>
359 .B lcp-max-configure \fI<n>
360 Set the maximum number of LCP configure-request transmissions to <n>
363 .B lcp-max-failure \fI<n>
364 Set the maximum number of LCP configure-NAKs returned before starting
365 to send configure-Rejects instead to <n> (default 10).
367 .B ipcp-restart \fI<n>
368 Set the IPCP restart interval (retransmission timeout) to <n> seconds
371 .B ipcp-max-terminate \fI<n>
372 Set the maximum number of IPCP terminate-request transmissions to <n>
375 .B ipcp-max-configure \fI<n>
376 Set the maximum number of IPCP configure-request transmissions to <n>
379 .B ipcp-max-failure \fI<n>
380 Set the maximum number of IPCP configure-NAKs returned before starting
381 to send configure-Rejects instead to <n> (default 10).
383 .B pap-restart \fI<n>
384 Set the PAP restart interval (retransmission timeout) to <n> seconds
387 .B pap-max-authreq \fI<n>
388 Set the maximum number of PAP authenticate-request transmissions to
391 .B chap-restart \fI<n>
392 Set the CHAP restart interval (retransmission timeout for challenges)
393 to <n> seconds (default 3).
395 .B chap-max-challenge \fI<n>
396 Set the maximum number of CHAP challenge transmissions to <n> (default
399 .B chap-interval \fI<n>
400 If this option is given,
402 will rechallenge the peer every <n> seconds.
407 will accept the peer's idea of our local IP address, even if the
408 local IP address was specified in an option.
410 .B ipcp-accept-remote
413 will accept the peer's idea of its (remote) IP address, even if the
414 remote IP address was specified in an option.
416 Options can be taken from files as well as the command line.
418 reads options from the files /etc/ppp/options and ~/.ppprc before
419 looking at the command line. An options file is parsed into a series
420 of words, delimited by whitespace. Whitespace can be included in a
421 word by enclosing the word in quotes ("). A backslash (\\) quotes the
422 following character. A hash (#) starts a comment, which continues
423 until the end of the line.
426 provides system administrators with sufficient access control that PPP
427 access to a server machine can be provided to legitimate users without
428 fear of compromising the security of the server or the network it's
429 on. In part this is provided by the /etc/ppp/options file, where the
430 administrator can place options to require authentication whenever
432 is run, and in part by the PAP and CHAP secrets files, where the
433 administrator can restrict the set of IP addresses which individual
436 The default behaviour of
438 is to agree to authenticate if requested, and to not
439 require authentication from the peer. However,
442 authenticate itself with a particular protocol if it has no secrets
443 which could be used to do so.
445 Authentication is based on secrets, which are selected from secrets
446 files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
447 Both secrets files have the same format, and both can store secrets
448 for several combinations of server (authenticating peer) and client
449 (peer being authenticated). Note that
452 and client, and that different protocols can be used in the two
453 directions if desired.
455 A secrets file is parsed into words as for a options file. A secret
456 is specified by a line containing at least 3 words, in the order
457 client, server, secret. Any following words on the same line are
458 taken to be a list of acceptable IP addresses for that client. If
459 there are only 3 words on the line, it is assumed that any IP address
460 is OK; to disallow all IP addresses, use "-". If the secret starts
461 with an `@', what follows is assumed to be the name of a file from
462 which to read the secret. A "*" as the client or server name matches
463 any name. When selecting a secret, \fIpppd\fR takes the best match, i.e.
464 the match with the fewest wildcards.
466 Thus a secrets file contains both secrets for use in authenticating
467 other hosts, plus secrets which we use for authenticating ourselves to
468 others. Which secret to use is chosen based on the names of the host
469 (the `local name') and its peer (the `remote name'). The local name
472 if the \fBusehostname\fR option is given,
473 then the local name is the hostname of this machine
474 (with the domain appended, if given)
476 else if the \fBname\fR option is given,
477 then use the argument of the first \fBname\fR option seen
479 else if the local IP address is specified with a hostname,
482 else use the hostname of this machine (with the domain appended, if given)
484 When authenticating ourselves using PAP, there is also a `username'
485 which is the local name by default, but can be set with the \fBuser\fR
486 option or the \fB+ua\fR option.
488 The remote name is set as follows:
490 if the \fBremotename\fR option is given,
491 then use the argument of the last \fBremotename\fR option seen
493 else if the remote IP address is specified with a hostname,
494 then use that host name
496 else the remote name is the null string "".
498 Secrets are selected from the PAP secrets file as follows:
501 For authenticating the peer, look for a secret with client ==
502 username specified in the PAP authenticate-request, and server ==
506 For authenticating ourselves to the peer, look for a secret with
507 client == our username, server == remote name.
509 When authenticating the peer with PAP, a secret of "" matches any
510 password supplied by the peer. If the password doesn't match the
511 secret, the password is encrypted using crypt() and checked against
512 the secret again; thus secrets for authenticating the peer can be
513 stored in encrypted form. If the \fBlogin\fR option was specified, the
514 username and password are also checked against the system password
515 database. Thus, the system administrator can set up the pap-secrets
516 file to allow PPP access only to certain users, and to restrict the
517 set of IP addresses that each user can use.
519 Secrets are selected from the CHAP secrets file as follows:
522 For authenticating the peer, look for a secret with client == name
523 specified in the CHAP-Response message, and server == local name.
526 For authenticating ourselves to the peer, look for a secret with
527 client == local name, and server == name specified in the
528 CHAP-Challenge message.
530 Authentication must be satisfactorily completed before IPCP (or any
531 other Network Control Protocol) can be started. If authentication
532 fails, \fIpppd\fR will terminated the link (by closing LCP). If IPCP
533 negotiates an unacceptable IP address for the remote host, IPCP will
534 be closed. IP packets can only be sent or received when IPCP is open.
536 In some cases it is desirable to allow some hosts which can't
537 authenticate themselves to connect and use one of a restricted set of
538 IP addresses, even when the local host generally requires
539 authentication. If the peer refuses to authenticate itself when
540 requested, \fIpppd\fR takes that as equivalent to authenticating with
541 PAP using the empty string for the username and password. Thus, by
542 adding a line to the pap-secrets file which specifies the empty string
543 for the client and password, it is possible to allow restricted access
544 to hosts which refuse to authenticate themselves.
547 When IPCP negotiation is completed successfully,
549 will inform the kernel of the local and remote IP addresses for the
550 ppp interface. This is sufficient to create a
551 host route to the remote end of the link, which will enable the peers
552 to exchange IP packets. Communication with other machines generally
553 requires further modification to routing tables and/or ARP (Address
554 Resolution Protocol) tables. In some cases this will be done
555 automatically through the actions of the \fIrouted\fR or \fIgated\fR
556 daemons, but in most cases some further intervention is required.
558 Sometimes it is desirable
559 to add a default route through the remote host, as in the case of a
560 machine whose only connection to the Internet is through the ppp
561 interface. The \fBdefaultroute\fR option causes \fIpppd\fR to create such a
562 default route when IPCP comes up, and delete it when the link is
565 In some cases it is desirable to use proxy ARP, for example on a
566 server machine connected to a LAN, in order to allow other hosts to
567 communicate with the remote host. The \fBproxyarp\fR option causes \fIpppd\fR
568 to look for a network interface on the same subnet as the remote host
569 (an interface supporting broadcast and ARP, which is up and not a
570 point-to-point or loopback interface). If found, \fIpppd\fR creates a
571 permanent, published ARP entry with the IP address of the remote host
572 and the hardware address of the network interface found.
575 In the simplest case, you can connect the serial ports of two machines
576 and issue a command like
578 pppd /dev/ttya 9600 passive
580 to each machine, assuming there is no \fIgetty\fR running on the
581 serial ports. If one machine has a \fIgetty\fR running, you can use
582 \fIkermit\fR or \fItip\fR on the other machine to log in to the first
583 machine and issue a command like
587 Then exit from the communications program (making sure the connection
588 isn't dropped), and issue a command like
592 The process of logging in to the other machine and starting \fIpppd\fR
593 can be automated by using the \fBconnect\fR option to run \fIchat\fR,
596 pppd /dev/ttya 38400 connect 'chat "" "" "login:" "username"
597 "Password:" "password" "% " "exec pppd passive"'
599 (Note however that running chat like this will leave the password
600 visible in the parameter list of pppd and chat.)
602 If your serial connection is any more complicated than a piece of
603 wire, you may need to arrange for some control characters to be
604 escaped. In particular, it is often useful to escape XON (^Q) and
605 XOFF (^S), using \fBasyncmap a0000\fR. If the path includes a telnet,
606 you probably should escape ^] as well (\fBasyncmap 200a0000\fR).
607 If the path includes an rlogin, you will need to use the \fBescape
608 ff\fR option on the end which is running the rlogin client, since many
609 rlogin implementations are not
610 transparent; they will remove the sequence [0xff, 0xff, 0x73, 0x73,
611 followed by any 8 bytes] from the stream.
614 Messages are sent to the syslog daemon using facility LOG_DAEMON.
615 (This can be overriden by recompiling \fIpppd\fR with the macro
616 LOG_PPP defined as the desired facility.) In order to see the error
617 and debug messages, you will need to edit your /etc/syslog.conf file
618 to direct the messages to the desired output device or file.
620 The \fBdebug\fR option causes the contents of all control packets sent
621 or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
622 This can be useful if the PPP negotiation does not succeed.
623 If debugging is enabled at compile time, the \fBdebug\fR option also
624 causes other debugging messages to be logged.
626 Debugging can also be enabled or disabled by sending a
629 process. This signal acts as a toggle.
632 .B /var/run/ppp\fIn\fB.pid \fR(BSD or Linux), \fB/etc/ppp/ppp\fIn\fB.pid \fR(others)
633 Process-ID for \fIpppd\fR process on ppp interface unit \fIn\fR.
636 A program or script which is executed when the link is available for
637 sending and receiving IP packets (that is, IPCP has come up). It is
638 executed with the parameters
640 \fIinterface-name tty-device speed local-IP-address
643 and with its standard input,
644 output and error streams redirected to \fB/dev/null\fR.
646 This program or script is executed with the same real and effective
647 user-ID as \fIpppd\fR, that is, at least the effective user-ID and
648 possibly the real user-ID will be \fBroot\fR. This is so that it can
649 be used to manipulate routes, run privileged daemons (e.g.
650 \fBsendmail\fR), etc. Be careful that the contents of the
651 /etc/ppp/ip-up and /etc/ppp/ip-down scripts do not compromise your
655 A program or script which is executed when the link is no longer
656 available for sending and receiving IP packets. This script can be
657 used for undoing the effects of the /etc/ppp/ip-up script. It is
658 invoked with the same parameters as the ip-up script, and the same
659 security considerations apply, since it is executed with the same
660 effective and real user-IDs as \fIpppd\fR.
662 .B /etc/ppp/pap-secrets
663 Usernames, passwords and IP addresses for PAP authentication.
665 .B /etc/ppp/chap-secrets
666 Names, secrets and IP addresses for CHAP authentication.
669 System default options for
671 read before user default options or command-line options.
674 User default options, read before command-line options.
676 .B /etc/ppp/options.\fIttyname
677 System default options for the serial port being used, read after
678 command-line options.
683 .I Compressing TCP/IP headers for low-speed serial links.
688 .I The MD5 Message-Digest Algorithm.
693 .I PPP Internet Protocol Control Protocol (IPCP).
697 Lloyd, B.; Simpson, W.A.
698 .I PPP authentication protocols.
703 .I The Point\-to\-Point Protocol (PPP).
708 .I PPP in HDLC Framing.
711 The following signals have the specified effect when sent to the
716 These signals cause \fBpppd\fR to terminate the link (by closing LCP),
717 restore the serial device settings, and exit.
720 This signal causes \fBpppd\fR to terminate the link, restore the
721 serial device settings, and close the serial device. If the
722 \fBpersist\fR option has been specified, \fBpppd\fR will try to reopen
723 the serial device and start another connection. Otherwise \fBpppd\fR
729 to renegotiate compression. This can be useful to re-enable
730 compression after it has been disabled as a result of a fatal
731 decompression error. With the BSD Compress scheme, fatal
732 decompression errors generally indicate a bug in one or other
741 Paul Mackerras (paulus@cs.anu.edu.au).
projects / ppp.git / blob