1 .\" manual page [] for pppd 2.3
2 .\" $Id: pppd.8,v 1.42 1999/08/04 15:53:13 johnsonm 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.
30 Pppd provides the basic LCP, authentication support, and an NCP for
31 establishing and configuring the Internet Protocol (IP) (called the IP
32 Control Protocol, IPCP).
33 .SH FREQUENTLY USED OPTIONS
36 Communicate over the named device. The string "/dev/" is prepended if
37 necessary. If no device name is given, or if the name of the terminal
38 connected to the standard input is given, pppd will use that terminal,
39 and will not fork to put itself in the background. A value for this
40 option from a privileged source cannot be overridden by a
44 Set the baud rate to <speed> (a decimal number). On systems such as
45 4.4BSD and NetBSD, any speed can be specified. Other systems
46 (e.g. SunOS) allow only a limited set of speeds.
49 Set the async character map to <map>. This map describes which
50 control characters cannot be successfully received over the serial
51 line. Pppd will ask the peer to send these characters as a 2-byte
52 escape sequence. The argument is a 32 bit hex number with each bit
53 representing a character to escape. Bit 0 (00000001) represents the
54 character 0x00; bit 31 (80000000) represents the character 0x1f or ^_.
55 If multiple \fIasyncmap\fR options are given, the values are ORed
56 together. If no \fIasyncmap\fR option is given, no async character
57 map will be negotiated for the receive direction; the peer should then
58 escape \fIall\fR control characters. To escape transmitted
59 characters, use the \fIescape\fR option.
62 Require the peer to authenticate itself before allowing network
63 packets to be sent or received. This option is the default if the
64 system has a default route. If neither this option nor the
65 \fInoauth\fR option is specified, pppd will only allow the peer to use
66 IP addresses to which the system does not already have a route.
69 Read options from the file /etc/ppp/peers/\fIname\fR. This file may
70 contain privileged options, such as \fInoauth\fR, even if pppd
71 is not being run by root. The \fIname\fR string may not begin with /
72 or include .. as a pathname component. The format of the options file
76 Use the executable or shell command specified by \fIscript\fR to set
77 up the serial line. This script would typically use the chat(8)
78 program to dial the modem and start the remote ppp session. A value
79 for this option from a privileged source cannot be overridden by a
83 Use hardware flow control (i.e. RTS/CTS) to control the flow of
84 data on the serial port. If neither the \fIcrtscts\fR, the
85 \fInocrtscts\fR, the \fIcdtrcts\fR nor the \fInocdtrcts\fR option
86 is given, the hardware flow control setting for the serial port is
88 Some serial ports (such as Macintosh serial ports) lack a true
89 RTS output. Such serial ports use this mode to implement
90 unidirectional flow control. The serial port will
91 suspend transmission when requested by the modem (via CTS)
92 but will be unable to request the modem stop sending to the
93 computer. This mode retains the ability to use DTR as
97 Use a non-standard hardware flow control (i.e. DTR/CTS) to control
98 the flow of data on the serial port. If neither the \fIcrtscts\fR,
99 the \fInocrtscts\fR, the \fIcdtrcts\fR nor the \fInocdtrcts\fR
100 option is given, the hardware flow control setting for the serial
101 port is left unchanged.
102 Some serial ports (such as Macintosh serial ports) lack a true
103 RTS output. Such serial ports use this mode to implement true
104 bi-directional flow control. The sacrifice is that this flow
105 control mode does not permit using DTR as a modem control line.
108 Add a default route to the system routing tables, using the peer as
109 the gateway, when IPCP negotiation is successfully completed.
110 This entry is removed when the PPP connection is broken. This option
111 is privileged if the \fInodefaultroute\fR option has been specified.
113 .B disconnect \fIscript
114 Run the executable or shell command specified by \fIscript\fR after
115 pppd has terminated the link. This script could, for example, issue
116 commands to the modem to cause it to hang up if hardware modem control
117 signals were not available. The disconnect script is not run if the
118 modem has already hung up. A value for this option from a privileged
119 source cannot be overridden by a non-privileged user.
121 .B escape \fIxx,yy,...
122 Specifies that certain characters should be escaped on transmission
123 (regardless of whether the peer requests them to be escaped with its
124 async control character map). The characters to be escaped are
125 specified as a list of hex numbers separated by commas. Note that
126 almost any character can be specified for the \fIescape\fR option,
127 unlike the \fIasyncmap\fR option which only allows control characters
128 to be specified. The characters which may not be escaped are those
129 with hex values 0x20 - 0x3f or 0x5e.
132 Read options from file \fIname\fR (the format is described below).
133 The file must be readable by the user who has invoked pppd.
136 Run the executable or shell command specified by \fIscript\fR to
137 initialize the serial line. This script would typically use the
138 chat(8) program to configure the modem to enable auto answer. A value
139 for this option from a privileged source cannot be overridden by a
143 Specifies that pppd should create a UUCP-style lock file for the
144 serial device to ensure exclusive access to the device.
147 Set the MRU [Maximum Receive Unit] value to \fIn\fR. Pppd
148 will ask the peer to send packets of no more than \fIn\fR bytes. The
149 minimum MRU value is 128. The default MRU value is 1500. A value of
150 296 is recommended for slow links (40 bytes for TCP/IP header + 256
154 Set the MTU [Maximum Transmit Unit] value to \fIn\fR. Unless the
155 peer requests a smaller value via MRU negotiation, pppd will
156 request that the kernel networking code send data packets of no more
157 than \fIn\fR bytes through the PPP network interface.
160 Enables the "passive" option in the LCP. With this option, pppd will
161 attempt to initiate a connection; if no reply is received from the
162 peer, pppd will then just wait passively for a valid LCP packet from
163 the peer, instead of exiting, as it would without this option.
166 .I <local_IP_address>\fB:\fI<remote_IP_address>
167 Set the local and/or remote interface IP addresses. Either one may be
168 omitted. The IP addresses can be specified with a host name or in
169 decimal dot notation (e.g. 150.234.56.78). The default local
170 address is the (first) IP address of the system (unless the
172 option is given). The remote address will be obtained from the peer
173 if not specified in any option. Thus, in simple cases, this option is
174 not required. If a local and/or remote IP address is specified with
176 will not accept a different value from the peer in the IPCP
177 negotiation, unless the \fIipcp-accept-local\fR and/or
178 \fIipcp-accept-remote\fR options are given, respectively.
180 .B active-filter \fIfilter-expression
181 Specifies a packet filter to be applied to data packets to determine
182 which packets are to be regarded as link activity, and therefore reset
183 the idle timer, or cause the link to be brought up in demand-dialling
184 mode. This option is useful in conjunction with the
185 \fBidle\fR option if there are packets being sent or received
186 regularly over the link (for example, routing information packets)
187 which would otherwise prevent the link from ever appearing to be idle.
188 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
189 except that qualifiers which are inappropriate for a PPP link, such as
190 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
191 expression should be enclosed in single-quotes to prevent whitespace
192 in the expression from being interpreted by the shell. This option
193 is currently only available under NetBSD, and then only
194 if both the kernel and pppd were compiled with PPP_FILTER defined.
197 Request that the peer compress packets that it sends, using the
198 BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
199 agree to compress packets sent to the peer with a maximum code size of
200 \fInt\fR bits. If \fInt\fR is not specified, it defaults to the value
201 given for \fInr\fR. Values in the range 9 to 15 may be used for
202 \fInr\fR and \fInt\fR; larger values give better compression but
203 consume more kernel memory for compression dictionaries.
204 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
205 compression in the corresponding direction. Use \fInobsdcomp\fR or
206 \fIbsdcomp 0\fR to disable BSD-Compress compression entirely.
208 .B chap-interval \fIn
209 If this option is given, pppd will rechallenge the peer every \fIn\fR
212 .B chap-max-challenge \fIn
213 Set the maximum number of CHAP challenge transmissions to \fIn\fR
217 Set the CHAP restart interval (retransmission timeout for challenges)
218 to \fIn\fR seconds (default 3).
221 Enables connection debugging facilities.
222 If this option is given, pppd will log the contents of all
223 control packets sent or received in a readable form. The packets are
224 logged through syslog with facility \fIdaemon\fR and level
225 \fIdebug\fR. This information can be directed to a file by setting up
226 /etc/syslog.conf appropriately (see syslog.conf(5)).
229 Disable asyncmap negotiation, forcing all control characters to be
230 escaped for both the transmit and the receive direction.
233 Disable MRU [Maximum Receive Unit] negotiation. With this option,
234 pppd will use the default MRU value of 1500 bytes for both the
235 transmit and receive direction.
238 Request that the peer compress packets that it sends, using the
239 Deflate scheme, with a maximum window size of \fI2**nr\fR bytes, and
240 agree to compress packets sent to the peer with a maximum window size
241 of \fI2**nt\fR bytes. If \fInt\fR is not specified, it defaults to
242 the value given for \fInr\fR. Values in the range 8 to 15 may be used
243 for \fInr\fR and \fInt\fR; larger values give better compression but
244 consume more kernel memory for compression dictionaries.
245 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
246 compression in the corresponding direction. Use \fInodeflate\fR or
247 \fIdeflate 0\fR to disable Deflate compression entirely. (Note: pppd
248 requests Deflate compression in preference to BSD-Compress if the peer
252 Initiate the link only on demand, i.e. when data traffic is present.
253 With this option, the remote IP address must be specified by the user
254 on the command line or in an options file. Pppd will initially
255 configure the interface and enable it for IP traffic without
256 connecting to the peer. When traffic is available, pppd will
257 connect to the peer and perform negotiation, authentication, etc.
258 When this is completed, pppd will commence passing data packets
259 (i.e., IP packets) across the link.
261 The \fIdemand\fR option implies the \fIpersist\fR option. If this
262 behaviour is not desired, use the \fInopersist\fR option after the
263 \fIdemand\fR option. The \fIidle\fR and \fIholdoff\fR
264 options are also useful in conjuction with the \fIdemand\fR option.
267 Append the domain name \fId\fR to the local host name for authentication
268 purposes. For example, if gethostname() returns the name porsche, but
269 the fully qualified domain name is porsche.Quotron.COM, you could
270 specify \fIdomain Quotron.COM\fR. Pppd would then use the name
271 \fIporsche.Quotron.COM\fR for looking up secrets in the secrets file,
272 and as the default name to send to the peer when authenticating itself
273 to the peer. This option is privileged.
276 When logging the contents of PAP packets, this option causes pppd to
277 exclude the password string from the log.
280 Specifies how many seconds to wait before re-initiating the link after
281 it terminates. This option only has any effect if the \fIpersist\fR
282 or \fIdemand\fR option is used. The holdoff period is not applied if
283 the link was terminated because it was idle.
286 Specifies that pppd should disconnect if the link is idle for \fIn\fR
287 seconds. The link is idle when no data packets (i.e. IP packets) are
288 being sent or received. Note: it is not advisable to use this option
289 with the \fIpersist\fR option without the \fIdemand\fR option.
290 If the \fBactive-filter\fR
291 option is given, data packets which are rejected by the specified
292 activity filter also count as the link being idle.
295 With this option, pppd will accept the peer's idea of our local IP
296 address, even if the local IP address was specified in an option.
298 .B ipcp-accept-remote
299 With this option, pppd will accept the peer's idea of its (remote) IP
300 address, even if the remote IP address was specified in an option.
302 .B ipcp-max-configure \fIn
303 Set the maximum number of IPCP configure-request transmissions to
304 \fIn\fR (default 10).
306 .B ipcp-max-failure \fIn
307 Set the maximum number of IPCP configure-NAKs returned before starting
308 to send configure-Rejects instead to \fIn\fR (default 10).
310 .B ipcp-max-terminate \fIn
311 Set the maximum number of IPCP terminate-request transmissions to
315 Set the IPCP restart interval (retransmission timeout) to \fIn\fR
319 Provides an extra parameter to the ip-up and ip-down scripts. If this
320 option is given, the \fIstring\fR supplied is given as the 6th
321 parameter to those scripts.
324 Enable the IPXCP and IPX protocols. This option is presently only
325 supported under Linux, and only if your kernel has been configured to
329 Set the IPX network number in the IPXCP configure request frame to
330 \fIn\fR, a hexadecimal number (without a leading 0x). There is no
331 valid default. If this option is not specified, the network number is
332 obtained from the peer. If the peer does not have the network number,
333 the IPX protocol will not be started.
335 .B ipx-node \fIn\fB:\fIm
336 Set the IPX node numbers. The two node numbers are separated from each
337 other with a colon character. The first number \fIn\fR is the local
338 node number. The second number \fIm\fR is the peer's node number. Each
339 node number is a hexadecimal number, at most 10 digits long. The node
340 numbers on the ipx-network must be unique. There is no valid
341 default. If this option is not specified then the node numbers are
342 obtained from the peer.
344 .B ipx-router-name \fI<string>
345 Set the name of the router. This is a string and is sent to the peer
349 Set the routing protocol to be received by this option. More than one
350 instance of \fIipx-routing\fR may be specified. The '\fInone\fR'
351 option (0) may be specified as the only instance of ipx-routing. The
352 values may be \fI0\fR for \fINONE\fR, \fI2\fR for \fIRIP/SAP\fR, and
353 \fI4\fR for \fINLSP\fR.
355 .B ipxcp-accept-local
356 Accept the peer's NAK for the node number specified in the ipx-node
357 option. If a node number was specified, and non-zero, the default is
358 to insist that the value be used. If you include this option then you
359 will permit the peer to override the entry of the node number.
361 .B ipxcp-accept-network
362 Accept the peer's NAK for the network number specified in the
363 ipx-network option. If a network number was specified, and non-zero, the
364 default is to insist that the value be used. If you include this
365 option then you will permit the peer to override the entry of the node
368 .B ipxcp-accept-remote
369 Use the peer's network number specified in the configure request
370 frame. If a node number was specified for the peer and this option was
371 not specified, the peer will be forced to use the value which you have
374 .B ipxcp-max-configure \fIn
375 Set the maximum number of IPXCP configure request frames which the
376 system will send to \fIn\fR. The default is 10.
378 .B ipxcp-max-failure \fIn
379 Set the maximum number of IPXCP NAK frames which the local system will
380 send before it rejects the options. The default value is 3.
382 .B ipxcp-max-terminate \fIn
383 Set the maximum nuber of IPXCP terminate request frames before the
384 local system considers that the peer is not listening to them. The
388 Enable debugging code in the kernel-level PPP driver. The argument
389 \fIn\fR is a number which is the sum of the following values: 1 to
390 enable general debug messages, 2 to request that the contents of
391 received packets be printed, and 4 to request that the contents of
392 transmitted packets be printed. On most systems, messages printed by
393 the kernel are logged by syslog(1) to a file as directed in the
394 /etc/syslog.conf configuration file.
396 .B lcp-echo-failure \fIn
397 If this option is given, pppd will presume the peer to be dead
398 if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
399 echo-reply. If this happens, pppd will terminate the
400 connection. Use of this option requires a non-zero value for the
401 \fIlcp-echo-interval\fR parameter. This option can be used to enable
402 pppd to terminate after the physical connection has been broken
403 (e.g., the modem has hung up) in situations where no hardware modem
404 control lines are available.
406 .B lcp-echo-interval \fIn
407 If this option is given, pppd will send an LCP echo-request frame to
408 the peer every \fIn\fR seconds. Normally the peer should respond to
409 the echo-request by sending an echo-reply. This option can be used
410 with the \fIlcp-echo-failure\fR option to detect that the peer is no
413 .B lcp-max-configure \fIn
414 Set the maximum number of LCP configure-request transmissions to
415 \fIn\fR (default 10).
417 .B lcp-max-failure \fIn
418 Set the maximum number of LCP configure-NAKs returned before starting
419 to send configure-Rejects instead to \fIn\fR (default 10).
421 .B lcp-max-terminate \fIn
422 Set the maximum number of LCP terminate-request transmissions to
426 Set the LCP restart interval (retransmission timeout) to \fIn\fR
430 Don't use the modem control lines. With this option, pppd will ignore
431 the state of the CD (Carrier Detect) signal from the modem and will
432 not change the state of the DTR (Data Terminal Ready) signal.
435 Send log messages to file descriptor \fIn\fR. Pppd will send log
436 messages to at most one file or file descriptor (as well as sending
437 the log messages to syslog), so this option and the \fBlogfile\fR
438 option are mutually exclusive. The default is for pppd to send log
439 messages to stdout (file descriptor 1), unless the serial port is
440 already open on stdout.
442 .B logfile \fIfilename
443 Append log messages to the file \fIfilename\fR (as well as sending the
444 log messages to syslog). The file is opened with the privileges of
445 the user who invoked pppd, in append mode.
448 Use the system password database for authenticating the peer using
449 PAP, and record the user in the system wtmp file. Note that the peer
450 must have an entry in the /etc/ppp/pap-secrets file as well as the
451 system password database to be allowed access.
454 Terminate the connection when it has been available for network
455 traffic for \fIn\fR seconds (i.e. \fIn\fR seconds after the first
456 network control protocol comes up).
459 Use the modem control lines. This option is the default. With this
460 option, pppd will wait for the CD (Carrier Detect) signal from the
461 modem to be asserted when opening the serial device (unless a connect
462 script is specified), and it will drop the DTR (Data Terminal Ready)
463 signal briefly when the connection is terminated and before executing
464 the connect script. On Ultrix, this option implies hardware flow
465 control, as for the \fIcrtscts\fR option.
468 If pppd is acting as a server for Microsoft Windows clients, this
469 option allows pppd to supply one or two DNS (Domain Name Server)
470 addresses to the clients. The first instance of this option specifies
471 the primary DNS address; the second instance (if given) specifies the
472 secondary DNS address. (This option was present in some older
473 versions of pppd under the name \fBdns-addr\fR.)
476 If pppd is acting as a server for Microsoft Windows or "Samba"
477 clients, this option allows pppd to supply one or two WINS (Windows
478 Internet Name Services) server addresses to the clients. The first
479 instance of this option specifies the primary WINS address; the second
480 instance (if given) specifies the secondary WINS address.
483 Set the name of the local system for authentication purposes to
484 \fIname\fR. This is a privileged option. With this option, pppd will
485 use lines in the secrets files which have \fIname\fR as the second
486 field when looking for a secret to use in authenticating the peer. In
487 addition, unless overridden with the \fIuser\fR option, \fIname\fR
488 will be used as the name to send to the peer when authenticating the
489 local system to the peer. (Note that pppd does not append the domain
493 Set the interface netmask to \fIn\fR, a 32 bit netmask in "decimal dot"
494 notation (e.g. 255.255.255.0). If this option is given, the value
495 specified is ORed with the default netmask. The default netmask is
496 chosen based on the negotiated remote IP address; it is the
497 appropriate network mask for the class of the remote IP address, ORed
498 with the netmasks for any non point-to-point network interfaces in the
499 system which are on the same network. (Note: on some platforms, pppd
500 will always use 255.255.255.255 for the netmask, if that is the only
501 appropriate value for a point-to-point interface.)
504 Disable Address/Control compression in both directions (send and
508 Do not require the peer to authenticate itself. This option is
512 Disables BSD-Compress compression; \fBpppd\fR will not request or
513 agree to compress packets using the BSD-Compress scheme.
516 Disable CCP (Compression Control Protocol) negotiation. This option
517 should only be required if the peer is buggy and gets confused by
518 requests from pppd for CCP negotiation.
521 Disable hardware flow control (i.e. RTS/CTS) on the serial port.
522 If neither the \fIcrtscts\fR nor the \fInocrtscts\fR nor the
523 \fIcdtrcts\fR nor the \fInodtrcts\fR option is given, the hardware
524 flow control setting for the serial port is left unchanged.
527 This option is a synonym for \fInocrtscts\fR. Either of these options will
528 disable both forms of hardware flow control.
531 Disable the \fIdefaultroute\fR option. The system administrator who
532 wishes to prevent users from creating default routes with pppd
533 can do so by placing this option in the /etc/ppp/options file.
536 Disables Deflate compression; pppd will not request or agree to
537 compress packets using the Deflate scheme.
540 Don't detach from the controlling terminal. Without this option, if a
541 serial device other than the terminal on the standard input is
542 specified, pppd will fork to become a background process.
545 Disable IPCP negotiation and IP communication. This option should
546 only be required if the peer is buggy and gets confused by requests
547 from pppd for IPCP negotiation.
550 Disables the default behaviour when no local IP address is specified,
551 which is to determine (if possible) the local IP address from the
552 hostname. With this option, the peer will have to supply the local IP
553 address during IPCP negotiation (unless it specified explicitly on the
554 command line or in an options file).
557 Disable the IPXCP and IPX protocols. This option should only be
558 required if the peer is buggy and gets confused by requests from pppd
559 for IPXCP negotiation.
562 Do not send log messages to a file or file descriptor. This option
563 cancels the \fBlogfd\fR and \fBlogfile\fR options.
565 Disable magic number negotiation. With this option, pppd cannot
566 detect a looped-back line. This option should only be needed if the
570 Disable protocol field compression negotiation in both the receive and
571 the transmit direction.
574 Exit once a connection has been made and terminated. This is the
575 default unless the \fIpersist\fR or \fIdemand\fR option has been
579 Do not accept or agree to Predictor-1 comprssion.
582 Disable the \fIproxyarp\fR option. The system administrator who
583 wishes to prevent users from creating proxy ARP entries with pppd can
584 do so by placing this option in the /etc/ppp/options file.
587 Normally, pppd requires a terminal device. With this option, pppd
588 will allocate itself a pseudo-tty master/slave pair and use the slave
589 as its terminal device. Pppd will create a child process to act as a
590 `character shunt' to transfer characters between the pseudo-tty master
591 and its standard input and output. Thus pppd will transmit characters
592 on its standard output and receive characters on its standard input
593 even if they are not terminal devices. This option increases the
594 latency and CPU overhead of transferring data over the ppp interface
595 as all of the characters sent and received must flow through the
596 character shunt process. An explicit device name may not be given if
600 Disable Van Jacobson style TCP/IP header compression in both the
601 transmit and the receive direction.
604 Disable the connection-ID compression option in Van Jacobson style
605 TCP/IP header compression. With this option, pppd will not omit the
606 connection-ID byte from Van Jacobson compressed TCP/IP headers, nor
607 ask the peer to do so.
610 Indicates that all secrets in the /etc/ppp/pap-secrets file which are
611 used for checking the identity of the peer are encrypted, and thus
612 pppd should not accept a password which, before encryption, is
613 identical to the secret from the /etc/ppp/pap-secrets file.
615 .B pap-max-authreq \fIn
616 Set the maximum number of PAP authenticate-request transmissions to
617 \fIn\fR (default 10).
620 Set the PAP restart interval (retransmission timeout) to \fIn\fR
624 Set the maximum time that pppd will wait for the peer to authenticate
625 itself with PAP to \fIn\fR seconds (0 means no limit).
627 .B pass-filter \fIfilter-expression
628 Specifies a packet filter to applied to data packets being sent or
629 received to determine which packets should be allowed to pass.
630 Packets which are rejected by the filter are silently discarded. This
631 option can be used to prevent specific network daemons (such as
632 routed) using up link bandwidth, or to provide a basic firewall
634 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
635 except that qualifiers which are inappropriate for a PPP link, such as
636 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
637 expression should be enclosed in single-quotes to prevent whitespace
638 in the expression from being interpreted by the shell. Note that it
639 is possible to apply different constraints to incoming and outgoing
640 packets using the \fBinbound\fR and \fBoutbound\fR qualifiers. This
641 option is currently only available under NetBSD, and then only if both
642 the kernel and pppd were compiled with PPP_FILTER defined.
645 Do not exit after a connection is terminated; instead try to reopen
649 Request that the peer compress frames that it sends using Predictor-1
650 compression, and agree to compress transmitted frames with Predictor-1
651 if requested. This option has no effect unless the kernel driver
652 supports Predictor-1 compression.
654 .B privgroup \fIgroup-name
655 Allows members of group \fIgroup-name\fR to use privileged options.
656 This is a privileged option. Use of this option requires care as
657 there is no guarantee that members of \fIgroup-name\fR cannot use pppd
658 to become root themselves. Consider it equivalent to putting the
659 members of \fIgroup-name\fR in the kmem or disk group.
662 Add an entry to this system's ARP [Address Resolution Protocol] table
663 with the IP address of the peer and the Ethernet address of this
664 system. This will have the effect of making the peer appear to other
665 systems to be on the local ethernet.
668 Specifies that the command \fIscript\fR is to be used to communicate
669 rather than a specific terminal device. Pppd will allocate itself a
670 pseudo-tty master/slave pair and use the slave as its terminal
671 device. The \fIscript\fR will be run in a child process with the
672 pseudo-tty master as its standard input and output. An explicit
673 device name may not be given if this option is used.
676 With this option, pppd will accept all control characters from the
677 peer, including those marked in the receive asyncmap. Without this
678 option, pppd will discard those characters as specified in RFC1662.
679 This option should only be needed if the peer is buggy.
681 .B record \fIfilename
682 Specifies that pppd should record all characters sent and received to
683 a file named \fIfilename\fR. This file is opened in append mode,
684 using the user's user-ID and permissions. This option is implemented
685 using a pseudo-tty and a process to transfer characters between the
686 pseudo-tty and the real serial device, so it will increase the latency
687 and CPU overhead of transferring data over the ppp interface. The
688 characters are stored in a tagged format with timestamps, which can be
689 displayed in readable form using the pppdump(8) program.
691 .B remotename \fIname
692 Set the assumed name of the remote system for authentication purposes
696 With this option, pppd will not agree to authenticate itself to the
700 With this option, pppd will not agree to authenticate itself to the
704 Require the peer to authenticate itself using CHAP [Challenge
705 Handshake Authentication Protocol] authentication.
708 Require the peer to authenticate itself using PAP [Password
709 Authentication Protocol] authentication.
712 With this option, pppd will not transmit LCP packets to initiate a
713 connection until a valid LCP packet is received from the peer (as for
714 the `passive' option with ancient versions of pppd).
717 Use synchronous HDLC serial encoding instead of asynchronous.
718 The device used by pppd with this option must have sync support.
719 Currently supports Microgate SyncLink adapters
720 under Linux and FreeBSD 2.2.8 and later.
723 With this option, pppd will detach from its controlling terminal once
724 it has successfully established the ppp connection (to the point where
725 the first network control protocol, usually the IP control protocol,
729 Enforce the use of the hostname (with domain name appended, if given)
730 as the name of the local system for authentication purposes (overrides
731 the \fIname\fR option). This option is not normally needed since the
732 \fIname\fR option is privileged.
735 Ask the peer for up to 2 DNS server addresses. The addresses supplied
736 by the peer (if any) are passed to the /etc/ppp/ip-up script in the
737 environment variables DNS1 and DNS2.
740 Sets the name used for authenticating the local system to the peer to
744 Sets the number of connection slots to be used by the Van Jacobson
745 TCP/IP header compression and decompression code to \fIn\fR, which
746 must be between 2 and 16 (inclusive).
749 Run the executable or shell command specified by \fIscript\fR before
750 initiating PPP negotiation, after the connect script (if any) has
751 completed. A value for this option from a privileged source cannot be
752 overridden by a non-privileged user.
755 Use software flow control (i.e. XON/XOFF) to control the flow of data on
758 Options can be taken from files as well as the command line. Pppd
759 reads options from the files /etc/ppp/options, ~/.ppprc and
760 /etc/ppp/options.\fIttyname\fR (in that order) before processing the
761 options on the command line. (In fact, the command-line options are
762 scanned to find the terminal name before the options.\fIttyname\fR
763 file is read.) In forming the name of the options.\fIttyname\fR file,
764 the initial /dev/ is removed from the terminal name, and any remaining
765 / characters are replaced with dots.
767 An options file is parsed into a series of words, delimited by
768 whitespace. Whitespace can be included in a word by enclosing the
769 word in double-quotes ("). A backslash (\\) quotes the following character.
770 A hash (#) starts a comment, which continues until the end of the
771 line. There is no restriction on using the \fIfile\fR or \fIcall\fR
772 options within an options file.
775 provides system administrators with sufficient access control that PPP
776 access to a server machine can be provided to legitimate users without
777 fear of compromising the security of the server or the network it's
778 on. This control is provided through restrictions on which IP
779 addresses the peer may use, based on its authenticated identity (if
780 any), and through restrictions on which options a non-privileged user
781 may use. Several of pppd's options are privileged, in particular
782 those which permit potentially insecure configurations; these options
783 are only accepted in files which are under the control of the system
784 administrator, or if pppd is being run by root.
786 The default behaviour of pppd is to allow an unauthenticated peer to
787 use a given IP address only if the system does not already have a
788 route to that IP address. For example, a system with a
789 permanent connection to the wider internet will normally have a
790 default route, and thus all peers will have to authenticate themselves
791 in order to set up a connection. On such a system, the \fIauth\fR
792 option is the default. On the other hand, a system where the
793 PPP link is the only connection to the internet will not normally have
794 a default route, so the peer will be able to use almost any IP address
795 without authenticating itself.
797 As indicated above, some security-sensitive options are privileged,
798 which means that they may not be used by an ordinary non-privileged
799 user running a setuid-root pppd, either on the command line, in the
800 user's ~/.ppprc file, or in an options file read using the \fIfile\fR
801 option. Privileged options may be used in /etc/ppp/options file or in
802 an options file read using the \fIcall\fR option. If pppd is being
803 run by the root user, privileged options can be used without
806 When opening the device, pppd uses either the invoking user's user ID
807 or the root UID (that is, 0), depending on whether the device name was
808 specified by the user or the system administrator. If the device name
809 comes from a privileged source, that is, /etc/ppp/options or an
810 options file read using the \fIcall\fR option, pppd uses full root
811 privileges when opening the device. Thus, by creating an appropriate
812 file under /etc/ppp/peers, the system administrator can allow users to
813 establish a ppp connection via a device which they would not normally
814 have permission to access. Otherwise pppd uses the invoking user's
815 real UID when opening the device.
817 Authentication is the process whereby one peer convinces the other of
818 its identity. This involves the first peer sending its name to the
819 other, together with some kind of secret information which could only
820 come from the genuine authorized user of that name. In such an
821 exchange, we will call the first peer the "client" and the other the
822 "server". The client has a name by which it identifies itself to the
823 server, and the server also has a name by which it identifies itself
824 to the client. Generally the genuine client shares some secret (or
825 password) with the server, and authenticates itself by proving that it
826 knows that secret. Very often, the names used for authentication
827 correspond to the internet hostnames of the peers, but this is not
830 At present, pppd supports two authentication protocols: the Password
831 Authentication Protocol (PAP) and the Challenge Handshake
832 Authentication Protocol (CHAP). PAP involves the client sending its
833 name and a cleartext password to the server to authenticate itself.
834 In contrast, the server initiates the CHAP authentication exchange by
835 sending a challenge to the client (the challenge packet includes the
836 server's name). The client must respond with a response which
837 includes its name plus a hash value derived from the shared secret and
838 the challenge, in order to prove that it knows the secret.
840 The PPP protocol, being symmetrical, allows both peers to require the
841 other to authenticate itself. In that case, two separate and
842 independent authentication exchanges will occur. The two exchanges
843 could use different authentication protocols, and in principle,
844 different names could be used in the two exchanges.
846 The default behaviour of pppd is to agree to authenticate if
847 requested, and to not require authentication from the peer. However,
848 pppd will not agree to authenticate itself with a particular protocol
849 if it has no secrets which could be used to do so.
851 Pppd stores secrets for use in authentication in secrets
852 files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
853 Both secrets files have the same format. The secrets files can
854 contain secrets for pppd to use in authenticating itself to other
855 systems, as well as secrets for pppd to use when authenticating other
858 Each line in a secrets file contains one secret. A given secret is
859 specific to a particular combination of client and server - it can
860 only be used by that client to authenticate itself to that server.
861 Thus each line in a secrets file has at least 3 fields: the name of
862 the client, the name of the server, and the secret. These fields may
863 be followed by a list of the IP addresses that the specified client
864 may use when connecting to the specified server.
866 A secrets file is parsed into words as for a options file, so the
867 client name, server name and secrets fields must each be one word,
868 with any embedded spaces or other special characters quoted or
869 escaped. Any following words on the same line are taken to be a list
870 of acceptable IP addresses for that client. If there are only 3 words
871 on the line, or if the first word is "-", then all IP addresses are
872 disallowed. To allow any address, use "*".
873 A word starting with "!" indicates that the
874 specified address is \fInot\fR acceptable. An address may be followed
875 by "/" and a number \fIn\fR, to indicate a whole subnet, i.e. all
876 addresses which have the same value in the most significant \fIn\fR
877 bits. Note that case is significant in the client and server names
880 If the secret starts with an `@', what follows is assumed to be the
881 name of a file from which to read the secret. A "*" as the client or
882 server name matches any name. When selecting a secret, pppd takes the
883 best match, i.e. the match with the fewest wildcards.
885 Thus a secrets file contains both secrets for use in authenticating
886 other hosts, plus secrets which we use for authenticating ourselves to
887 others. When pppd is authenticating the peer (checking the peer's
888 identity), it chooses a secret with the peer's name in the first
889 field and the name of the local system in the second field. The
890 name of the local system defaults to the hostname, with the domain
891 name appended if the \fIdomain\fR option is used. This default can be
892 overridden with the \fIname\fR option, except when the
893 \fIusehostname\fR option is used.
895 When pppd is choosing a secret to use in authenticating itself to the
896 peer, it first determines what name it is going to use to identify
897 itself to the peer. This name can be specified by the user with the
898 \fIuser\fR option. If this option is not used, the name defaults to
899 the name of the local system, determined as described in the previous
900 paragraph. Then pppd looks for a secret with this name in the first
901 field and the peer's name in the second field. Pppd will know the
902 name of the peer if CHAP authentication is being used, because the
903 peer will have sent it in the challenge packet. However, if PAP is being
904 used, pppd will have to determine the peer's name from the options
905 specified by the user. The user can specify the peer's name directly
906 with the \fIremotename\fR option. Otherwise, if the remote IP address
907 was specified by a name (rather than in numeric form), that name will
908 be used as the peer's name. Failing that, pppd will use the null
909 string as the peer's name.
911 When authenticating the peer with PAP, the supplied password is first
912 compared with the secret from the secrets file. If the password
913 doesn't match the secret, the password is encrypted using crypt() and
914 checked against the secret again. Thus secrets for authenticating the
915 peer can be stored in encrypted form if desired. If the
916 \fIpapcrypt\fR option is given, the first (unencrypted) comparison is
917 omitted, for better security.
919 Furthermore, if the \fIlogin\fR option was specified, the username and
920 password are also checked against the system password database. Thus,
921 the system administrator can set up the pap-secrets file to allow PPP
922 access only to certain users, and to restrict the set of IP addresses
923 that each user can use. Typically, when using the \fIlogin\fR option,
924 the secret in /etc/ppp/pap-secrets would be "", which will match any
925 password supplied by the peer. This avoids the need to have the same
926 secret in two places.
928 Authentication must be satisfactorily completed before IPCP (or any
929 other Network Control Protocol) can be started. If the peer is
930 required to authenticate itself, and fails to do so, pppd will
931 terminated the link (by closing LCP). If IPCP negotiates an
932 unacceptable IP address for the remote host, IPCP will be closed. IP
933 packets can only be sent or received when IPCP is open.
935 In some cases it is desirable to allow some hosts which can't
936 authenticate themselves to connect and use one of a restricted set of
937 IP addresses, even when the local host generally requires
938 authentication. If the peer refuses to authenticate itself when
939 requested, pppd takes that as equivalent to authenticating with PAP
940 using the empty string for the username and password. Thus, by adding
941 a line to the pap-secrets file which specifies the empty string for
942 the client and password, it is possible to allow restricted access to
943 hosts which refuse to authenticate themselves.
946 When IPCP negotiation is completed successfully, pppd will inform the
947 kernel of the local and remote IP addresses for the ppp interface.
948 This is sufficient to create a host route to the remote end of the
949 link, which will enable the peers to exchange IP packets.
950 Communication with other machines generally requires further
951 modification to routing tables and/or ARP (Address Resolution
952 Protocol) tables. In most cases the \fIdefaultroute\fR and/or
953 \fIproxyarp\fR options are sufficient for this, but in some cases
954 further intervention is required. The /etc/ppp/ip-up script can be
957 Sometimes it is desirable to add a default route through the remote
958 host, as in the case of a machine whose only connection to the
959 Internet is through the ppp interface. The \fIdefaultroute\fR option
960 causes pppd to create such a default route when IPCP comes up, and
961 delete it when the link is terminated.
963 In some cases it is desirable to use proxy ARP, for example on a
964 server machine connected to a LAN, in order to allow other hosts to
965 communicate with the remote host. The \fIproxyarp\fR option causes
966 pppd to look for a network interface on the same subnet as the remote
967 host (an interface supporting broadcast and ARP, which is up and not a
968 point-to-point or loopback interface). If found, pppd creates a
969 permanent, published ARP entry with the IP address of the remote host
970 and the hardware address of the network interface found.
972 When the \fIdemand\fR option is used, the interface IP addresses have
973 already been set at the point when IPCP comes up. If pppd has not
974 been able to negotiate the same addresses that it used to configure
975 the interface (for example when the peer is an ISP that uses dynamic
976 IP address assignment), pppd has to change the interface IP addresses
977 to the negotiated addresses. This may disrupt existing connections,
978 and the use of demand dialling with peers that do dynamic IP address
979 assignment is not recommended.
982 The following examples assume that the /etc/ppp/options file contains
983 the \fIauth\fR option (as in the default /etc/ppp/options file in the
986 Probably the most common use of pppd is to dial out to an ISP. This
987 can be done with a command such as
991 where the /etc/ppp/peers/isp file is set up by the system
992 administrator to contain something like this:
996 connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
1000 In this example, we are using chat to dial the ISP's modem and go
1001 through any logon sequence required. The /etc/ppp/chat-isp file
1002 contains the script used by chat; it could for example contain
1003 something like this:
1015 ABORT "Username/Password Incorrect"
1023 "name:" "^Umyuserid"
1025 "word:" "\\qmypassword"
1031 See the chat(8) man page for details of chat scripts.
1033 Pppd can also be used to provide a dial-in ppp service for users. If
1034 the users already have login accounts, the simplest way to set up the
1035 ppp service is to let the users log in to their accounts and run pppd
1036 (installed setuid-root) with a command such as
1040 To allow a user to use the PPP facilities, you need to allocate an IP
1041 address for that user's machine and create an entry in
1042 /etc/ppp/pap-secrets or /etc/ppp/chap-secrets (depending on which
1043 authentication method the PPP implementation on the user's machine
1044 supports), so that the user's
1045 machine can authenticate itself. For example, if Joe has a machine
1046 called "joespc" which is to be allowed to dial in to the machine
1047 called "server" and use the IP address joespc.my.net, you would add an
1048 entry like this to /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:
1050 joespc server "joe's secret" joespc.my.net
1052 Alternatively, you can create a username called (for example) "ppp",
1053 whose login shell is pppd and whose home directory is /etc/ppp.
1054 Options to be used when pppd is run this way can be put in
1057 If your serial connection is any more complicated than a piece of
1058 wire, you may need to arrange for some control characters to be
1059 escaped. In particular, it is often useful to escape XON (^Q) and
1060 XOFF (^S), using \fIasyncmap a0000\fR. If the path includes a telnet,
1061 you probably should escape ^] as well (\fIasyncmap 200a0000\fR). If
1062 the path includes an rlogin, you will need to use the \fIescape ff\fR
1063 option on the end which is running the rlogin client, since many
1064 rlogin implementations are not transparent; they will remove the
1065 sequence [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the
1069 Messages are sent to the syslog daemon using facility LOG_DAEMON.
1070 (This can be overriden by recompiling pppd with the macro
1071 LOG_PPP defined as the desired facility.) In order to see the error
1072 and debug messages, you will need to edit your /etc/syslog.conf file
1073 to direct the messages to the desired output device or file.
1075 The \fIdebug\fR option causes the contents of all control packets sent
1076 or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
1077 This can be useful if the PPP negotiation does not succeed or if
1078 authentication fails.
1079 If debugging is enabled at compile time, the \fIdebug\fR option also
1080 causes other debugging messages to be logged.
1082 Debugging can also be enabled or disabled by sending a SIGUSR1 signal
1083 to the pppd process. This signal acts as a toggle.
1085 The exit status of pppd is set to indicate whether any error was
1086 detected, or the reason for the link being terminated. The values
1090 Pppd has detached, or otherwise the connection was successfully
1091 established and terminated at the peer's request.
1094 An immediately fatal error of some kind occurred, such as an essential
1095 system call failing, or running out of virtual memory.
1098 An error was detected in processing the options given, such as two
1099 mutually exclusive options being used.
1102 Pppd is not setuid-root and the invoking user is not root.
1105 The kernel does not support PPP, for example, the PPP kernel driver is
1106 not included or cannot be loaded.
1109 Pppd terminated because it was sent a SIGINT, SIGTERM or SIGHUP
1113 The serial port could not be locked.
1116 The serial port could not be opened.
1119 The connect script failed (returned a non-zero exit status).
1122 The command specified as the argument to the \fIpty\fR option could
1126 The PPP negotiation failed, that is, it didn't reach the point where
1127 at least one network protocol (e.g. IP) was running.
1130 The peer system failed (or refused) to authenticate itself.
1133 The link was established successfully and terminated because it was
1137 The link was established successfully and terminated because the
1138 connect time limit was reached.
1141 Callback was negotiated and an incoming call should arrive shortly.
1144 The link was terminated because the peer is not responding to echo
1148 The link was terminated by the modem hanging up.
1151 The PPP negotiation failed because serial loopback was detected.
1154 The init script failed (returned a non-zero exit status).
1156 Pppd invokes scripts at various stages in its processing which can be
1157 used to perform site-specific ancillary processing. These scripts are
1158 usually shell scripts, but could be executable code files instead.
1159 Pppd does not wait for the scripts to finish. The scripts are
1160 executed as root (with the real and effective user-id set to 0), so
1161 that they can do things such as update routing tables or run
1162 privileged daemons. Be careful that the contents of these scripts do
1163 not compromise your system's security. Pppd runs the scripts with
1164 standard input, output and error redirected to /dev/null, and with an
1165 environment that is empty except for some environment variables that
1166 give information about the link. The environment variables that pppd
1170 The name of the serial tty device being used.
1173 The name of the network interface being used.
1176 The IP address for the local end of the link. This is only set when
1180 The IP address for the remote end of the link. This is only set when
1184 The authenticated name of the peer. This is only set if the peer
1185 authenticates itself.
1188 The baud rate of the tty device.
1191 The real user-id of the user who invoked pppd.
1194 The username of the real user-id that invoked pppd. This is always set.
1196 For the ip-down and auth-down scripts, pppd also sets the following
1197 variables giving statistics for the connection:
1200 The number of seconds from when the PPP negotiation started until the
1201 connection was terminated.
1204 The number of bytes sent (at the level of the serial port) during the
1208 The number of bytes received (at the level of the serial port) during
1211 Pppd invokes the following scripts, if they exist. It is not an error
1212 if they don't exist.
1215 A program or script which is executed after the remote system
1216 successfully authenticates itself. It is executed with the parameters
1218 \fIinterface-name peer-name user-name tty-device speed\fR
1220 Note that this script is not executed if the peer doesn't authenticate
1221 itself, for example when the \fInoauth\fR option is used.
1223 .B /etc/ppp/auth-down
1224 A program or script which is executed when the link goes down, if
1225 /etc/ppp/auth-up was previously executed. It is executed in the same
1226 manner with the same parameters as /etc/ppp/auth-up.
1229 A program or script which is executed when the link is available for
1230 sending and receiving IP packets (that is, IPCP has come up). It is
1231 executed with the parameters
1233 \fIinterface-name tty-device speed local-IP-address
1234 remote-IP-address ipparam\fR
1237 A program or script which is executed when the link is no longer
1238 available for sending and receiving IP packets. This script can be
1239 used for undoing the effects of the /etc/ppp/ip-up script. It is
1240 invoked in the same manner and with the same parameters as the ip-up
1244 A program or script which is executed when the link is available for
1245 sending and receiving IPX packets (that is, IPXCP has come up). It is
1246 executed with the parameters
1248 \fIinterface-name tty-device speed network-number local-IPX-node-address
1249 remote-IPX-node-address local-IPX-routing-protocol remote-IPX-routing-protocol
1250 local-IPX-router-name remote-IPX-router-name ipparam pppd-pid\fR
1252 The local-IPX-routing-protocol and remote-IPX-routing-protocol field
1253 may be one of the following:
1255 NONE to indicate that there is no routing protocol
1257 RIP to indicate that RIP/SAP should be used
1259 NLSP to indicate that Novell NLSP should be used
1261 RIP NLSP to indicate that both RIP/SAP and NLSP should be used
1263 .B /etc/ppp/ipx-down
1264 A program or script which is executed when the link is no longer
1265 available for sending and receiving IPX packets. This script can be
1266 used for undoing the effects of the /etc/ppp/ipx-up script. It is
1267 invoked in the same manner and with the same parameters as the ipx-up
1271 .B /var/run/ppp\fIn\fB.pid \fR(BSD or Linux), \fB/etc/ppp/ppp\fIn\fB.pid \fR(others)
1272 Process-ID for pppd process on ppp interface unit \fIn\fR.
1274 .B /etc/ppp/pap-secrets
1275 Usernames, passwords and IP addresses for PAP authentication. This
1276 file should be owned by root and not readable or writable by any other
1277 user. Pppd will log a warning if this is not the case.
1279 .B /etc/ppp/chap-secrets
1280 Names, secrets and IP addresses for CHAP authentication. As for
1281 /etc/ppp/pap-secrets, this file should be owned by root and not
1282 readable or writable by any other user. Pppd will log a warning if
1283 this is not the case.
1286 System default options for pppd, read before user default options or
1287 command-line options.
1290 User default options, read before /etc/ppp/options.\fIttyname\fR.
1292 .B /etc/ppp/options.\fIttyname
1293 System default options for the serial port being used, read after
1294 ~/.ppprc. In forming the \fIttyname\fR part of this
1295 filename, an initial /dev/ is stripped from the port name (if
1296 present), and any slashes in the remaining part are converted to
1300 A directory containing options files which may contain privileged
1301 options, even if pppd was invoked by a user other than root. The
1302 system administrator can create options files in this directory to
1303 permit non-privileged users to dial out without requiring the peer to
1304 authenticate, but only to certain trusted peers.
1309 \fICompressing TCP/IP headers for low-speed serial links.\fR
1314 .I The MD5 Message-Digest Algorithm.
1319 .I PPP Internet Protocol Control Protocol (IPCP).
1323 Lloyd, B.; Simpson, W.A.
1324 .I PPP authentication protocols.
1329 .I The Point\-to\-Point Protocol (PPP).
1334 .I PPP in HDLC-like Framing.
1337 The following signals have the specified effect when sent to pppd.
1340 These signals cause pppd to terminate the link (by closing LCP),
1341 restore the serial device settings, and exit.
1344 This signal causes pppd to terminate the link, restore the serial
1345 device settings, and close the serial device. If the \fIpersist\fR or
1346 \fIdemand\fR option has been specified, pppd will try to reopen the
1347 serial device and start another connection (after the holdoff period).
1348 Otherwise pppd will exit. If this signal is received during the
1349 holdoff period, it causes pppd to end the holdoff period immediately.
1352 This signal toggles the state of the \fIdebug\fR option.
1355 This signal causes pppd to renegotiate compression. This can be
1356 useful to re-enable compression after it has been disabled as a result
1357 of a fatal decompression error. (Fatal decompression errors generally
1358 indicate a bug in one or other implementation.)
1361 Paul Mackerras (Paul.Mackerras@cs.anu.edu.au), based on earlier work by
projects / ppp.git / blob