1 .\" manual page [] for pppd 2.3
2 .\" $Id: pppd.8,v 1.39 1999/04/16 11:34:45 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.
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 Specifies that pppd should create a UUCP-style lock file for the
137 serial device to ensure exclusive access to the device.
140 Set the MRU [Maximum Receive Unit] value to \fIn\fR. Pppd
141 will ask the peer to send packets of no more than \fIn\fR bytes. The
142 minimum MRU value is 128. The default MRU value is 1500. A value of
143 296 is recommended for slow links (40 bytes for TCP/IP header + 256
147 Set the MTU [Maximum Transmit Unit] value to \fIn\fR. Unless the
148 peer requests a smaller value via MRU negotiation, pppd will
149 request that the kernel networking code send data packets of no more
150 than \fIn\fR bytes through the PPP network interface.
153 Enables the "passive" option in the LCP. With this option, pppd will
154 attempt to initiate a connection; if no reply is received from the
155 peer, pppd will then just wait passively for a valid LCP packet from
156 the peer, instead of exiting, as it would without this option.
159 .I <local_IP_address>\fB:\fI<remote_IP_address>
160 Set the local and/or remote interface IP addresses. Either one may be
161 omitted. The IP addresses can be specified with a host name or in
162 decimal dot notation (e.g. 150.234.56.78). The default local
163 address is the (first) IP address of the system (unless the
165 option is given). The remote address will be obtained from the peer
166 if not specified in any option. Thus, in simple cases, this option is
167 not required. If a local and/or remote IP address is specified with
169 will not accept a different value from the peer in the IPCP
170 negotiation, unless the \fIipcp-accept-local\fR and/or
171 \fIipcp-accept-remote\fR options are given, respectively.
173 .B active-filter \fIfilter-expression
174 Specifies a packet filter to be applied to data packets to determine
175 which packets are to be regarded as link activity, and therefore reset
176 the idle timer, or cause the link to be brought up in demand-dialling
177 mode. This option is useful in conjunction with the
178 \fBidle\fR option if there are packets being sent or received
179 regularly over the link (for example, routing information packets)
180 which would otherwise prevent the link from ever appearing to be idle.
181 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
182 except that qualifiers which are inappropriate for a PPP link, such as
183 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
184 expression should be enclosed in single-quotes to prevent whitespace
185 in the expression from being interpreted by the shell. This option
186 is currently only available under NetBSD, and then only
187 if both the kernel and pppd were compiled with PPP_FILTER defined.
190 Request that the peer compress packets that it sends, using the
191 BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
192 agree to compress packets sent to the peer with a maximum code size of
193 \fInt\fR bits. If \fInt\fR is not specified, it defaults to the value
194 given for \fInr\fR. Values in the range 9 to 15 may be used for
195 \fInr\fR and \fInt\fR; larger values give better compression but
196 consume more kernel memory for compression dictionaries.
197 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
198 compression in the corresponding direction. Use \fInobsdcomp\fR or
199 \fIbsdcomp 0\fR to disable BSD-Compress compression entirely.
201 .B chap-interval \fIn
202 If this option is given, pppd will rechallenge the peer every \fIn\fR
205 .B chap-max-challenge \fIn
206 Set the maximum number of CHAP challenge transmissions to \fIn\fR
210 Set the CHAP restart interval (retransmission timeout for challenges)
211 to \fIn\fR seconds (default 3).
214 Enables connection debugging facilities.
215 If this option is given, pppd will log the contents of all
216 control packets sent or received in a readable form. The packets are
217 logged through syslog with facility \fIdaemon\fR and level
218 \fIdebug\fR. This information can be directed to a file by setting up
219 /etc/syslog.conf appropriately (see syslog.conf(5)).
222 Disable asyncmap negotiation, forcing all control characters to be
223 escaped for both the transmit and the receive direction.
226 Disable MRU [Maximum Receive Unit] negotiation. With this option,
227 pppd will use the default MRU value of 1500 bytes for both the
228 transmit and receive direction.
231 Request that the peer compress packets that it sends, using the
232 Deflate scheme, with a maximum window size of \fI2**nr\fR bytes, and
233 agree to compress packets sent to the peer with a maximum window size
234 of \fI2**nt\fR bytes. If \fInt\fR is not specified, it defaults to
235 the value given for \fInr\fR. Values in the range 8 to 15 may be used
236 for \fInr\fR and \fInt\fR; larger values give better compression but
237 consume more kernel memory for compression dictionaries.
238 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
239 compression in the corresponding direction. Use \fInodeflate\fR or
240 \fIdeflate 0\fR to disable Deflate compression entirely. (Note: pppd
241 requests Deflate compression in preference to BSD-Compress if the peer
245 Initiate the link only on demand, i.e. when data traffic is present.
246 With this option, the remote IP address must be specified by the user
247 on the command line or in an options file. Pppd will initially
248 configure the interface and enable it for IP traffic without
249 connecting to the peer. When traffic is available, pppd will
250 connect to the peer and perform negotiation, authentication, etc.
251 When this is completed, pppd will commence passing data packets
252 (i.e., IP packets) across the link.
254 The \fIdemand\fR option implies the \fIpersist\fR option. If this
255 behaviour is not desired, use the \fInopersist\fR option after the
256 \fIdemand\fR option. The \fIidle\fR and \fIholdoff\fR
257 options are also useful in conjuction with the \fIdemand\fR option.
260 Append the domain name \fId\fR to the local host name for authentication
261 purposes. For example, if gethostname() returns the name porsche, but
262 the fully qualified domain name is porsche.Quotron.COM, you could
263 specify \fIdomain Quotron.COM\fR. Pppd would then use the name
264 \fIporsche.Quotron.COM\fR for looking up secrets in the secrets file,
265 and as the default name to send to the peer when authenticating itself
266 to the peer. This option is privileged.
269 When logging the contents of PAP packets, this option causes pppd to
270 exclude the password string from the log.
273 Specifies how many seconds to wait before re-initiating the link after
274 it terminates. This option only has any effect if the \fIpersist\fR
275 or \fIdemand\fR option is used. The holdoff period is not applied if
276 the link was terminated because it was idle.
279 Specifies that pppd should disconnect if the link is idle for \fIn\fR
280 seconds. The link is idle when no data packets (i.e. IP packets) are
281 being sent or received. Note: it is not advisable to use this option
282 with the \fIpersist\fR option without the \fIdemand\fR option.
283 If the \fBactive-filter\fR
284 option is given, data packets which are rejected by the specified
285 activity filter also count as the link being idle.
288 With this option, pppd will accept the peer's idea of our local IP
289 address, even if the local IP address was specified in an option.
291 .B ipcp-accept-remote
292 With this option, pppd will accept the peer's idea of its (remote) IP
293 address, even if the remote IP address was specified in an option.
295 .B ipcp-max-configure \fIn
296 Set the maximum number of IPCP configure-request transmissions to
297 \fIn\fR (default 10).
299 .B ipcp-max-failure \fIn
300 Set the maximum number of IPCP configure-NAKs returned before starting
301 to send configure-Rejects instead to \fIn\fR (default 10).
303 .B ipcp-max-terminate \fIn
304 Set the maximum number of IPCP terminate-request transmissions to
308 Set the IPCP restart interval (retransmission timeout) to \fIn\fR
312 Provides an extra parameter to the ip-up and ip-down scripts. If this
313 option is given, the \fIstring\fR supplied is given as the 6th
314 parameter to those scripts.
317 Enable the IPXCP and IPX protocols. This option is presently only
318 supported under Linux, and only if your kernel has been configured to
322 Set the IPX network number in the IPXCP configure request frame to
323 \fIn\fR, a hexadecimal number (without a leading 0x). There is no
324 valid default. If this option is not specified, the network number is
325 obtained from the peer. If the peer does not have the network number,
326 the IPX protocol will not be started.
328 .B ipx-node \fIn\fB:\fIm
329 Set the IPX node numbers. The two node numbers are separated from each
330 other with a colon character. The first number \fIn\fR is the local
331 node number. The second number \fIm\fR is the peer's node number. Each
332 node number is a hexadecimal number, at most 10 digits long. The node
333 numbers on the ipx-network must be unique. There is no valid
334 default. If this option is not specified then the node numbers are
335 obtained from the peer.
337 .B ipx-router-name \fI<string>
338 Set the name of the router. This is a string and is sent to the peer
342 Set the routing protocol to be received by this option. More than one
343 instance of \fIipx-routing\fR may be specified. The '\fInone\fR'
344 option (0) may be specified as the only instance of ipx-routing. The
345 values may be \fI0\fR for \fINONE\fR, \fI2\fR for \fIRIP/SAP\fR, and
346 \fI4\fR for \fINLSP\fR.
348 .B ipxcp-accept-local
349 Accept the peer's NAK for the node number specified in the ipx-node
350 option. If a node number was specified, and non-zero, the default is
351 to insist that the value be used. If you include this option then you
352 will permit the peer to override the entry of the node number.
354 .B ipxcp-accept-network
355 Accept the peer's NAK for the network number specified in the
356 ipx-network option. If a network number was specified, and non-zero, the
357 default is to insist that the value be used. If you include this
358 option then you will permit the peer to override the entry of the node
361 .B ipxcp-accept-remote
362 Use the peer's network number specified in the configure request
363 frame. If a node number was specified for the peer and this option was
364 not specified, the peer will be forced to use the value which you have
367 .B ipxcp-max-configure \fIn
368 Set the maximum number of IPXCP configure request frames which the
369 system will send to \fIn\fR. The default is 10.
371 .B ipxcp-max-failure \fIn
372 Set the maximum number of IPXCP NAK frames which the local system will
373 send before it rejects the options. The default value is 3.
375 .B ipxcp-max-terminate \fIn
376 Set the maximum nuber of IPXCP terminate request frames before the
377 local system considers that the peer is not listening to them. The
381 Enable debugging code in the kernel-level PPP driver. The argument
382 \fIn\fR is a number which is the sum of the following values: 1 to
383 enable general debug messages, 2 to request that the contents of
384 received packets be printed, and 4 to request that the contents of
385 transmitted packets be printed. On most systems, messages printed by
386 the kernel are logged by syslog(1) to a file as directed in the
387 /etc/syslog.conf configuration file.
389 .B lcp-echo-failure \fIn
390 If this option is given, pppd will presume the peer to be dead
391 if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
392 echo-reply. If this happens, pppd will terminate the
393 connection. Use of this option requires a non-zero value for the
394 \fIlcp-echo-interval\fR parameter. This option can be used to enable
395 pppd to terminate after the physical connection has been broken
396 (e.g., the modem has hung up) in situations where no hardware modem
397 control lines are available.
399 .B lcp-echo-interval \fIn
400 If this option is given, pppd will send an LCP echo-request frame to
401 the peer every \fIn\fR seconds. Normally the peer should respond to
402 the echo-request by sending an echo-reply. This option can be used
403 with the \fIlcp-echo-failure\fR option to detect that the peer is no
406 .B lcp-max-configure \fIn
407 Set the maximum number of LCP configure-request transmissions to
408 \fIn\fR (default 10).
410 .B lcp-max-failure \fIn
411 Set the maximum number of LCP configure-NAKs returned before starting
412 to send configure-Rejects instead to \fIn\fR (default 10).
414 .B lcp-max-terminate \fIn
415 Set the maximum number of LCP terminate-request transmissions to
419 Set the LCP restart interval (retransmission timeout) to \fIn\fR
423 Don't use the modem control lines. With this option, pppd will ignore
424 the state of the CD (Carrier Detect) signal from the modem and will
425 not change the state of the DTR (Data Terminal Ready) signal.
428 Use the system password database for authenticating the peer using
429 PAP, and record the user in the system wtmp file. Note that the peer
430 must have an entry in the /etc/ppp/pap-secrets file as well as the
431 system password database to be allowed access.
434 Terminate the connection when it has been available for network
435 traffic for \fIn\fR seconds (i.e. \fIn\fR seconds after the first
436 network control protocol comes up).
439 Use the modem control lines. This option is the default. With this
440 option, pppd will wait for the CD (Carrier Detect) signal from the
441 modem to be asserted when opening the serial device (unless a connect
442 script is specified), and it will drop the DTR (Data Terminal Ready)
443 signal briefly when the connection is terminated and before executing
444 the connect script. On Ultrix, this option implies hardware flow
445 control, as for the \fIcrtscts\fR option.
448 If pppd is acting as a server for Microsoft Windows clients, this
449 option allows pppd to supply one or two DNS (Domain Name Server)
450 addresses to the clients. The first instance of this option specifies
451 the primary DNS address; the second instance (if given) specifies the
452 secondary DNS address. (This option was present in some older
453 versions of pppd under the name \fBdns-addr\fR.)
456 If pppd is acting as a server for Microsoft Windows or "Samba"
457 clients, this option allows pppd to supply one or two WINS (Windows
458 Internet Name Services) server addresses to the clients. The first
459 instance of this option specifies the primary WINS address; the second
460 instance (if given) specifies the secondary WINS address.
463 Set the name of the local system for authentication purposes to
464 \fIname\fR. This is a privileged option. With this option, pppd will
465 use lines in the secrets files which have \fIname\fR as the second
466 field when looking for a secret to use in authenticating the peer. In
467 addition, unless overridden with the \fIuser\fR option, \fIname\fR
468 will be used as the name to send to the peer when authenticating the
469 local system to the peer. (Note that pppd does not append the domain
473 Set the interface netmask to \fIn\fR, a 32 bit netmask in "decimal dot"
474 notation (e.g. 255.255.255.0). If this option is given, the value
475 specified is ORed with the default netmask. The default netmask is
476 chosen based on the negotiated remote IP address; it is the
477 appropriate network mask for the class of the remote IP address, ORed
478 with the netmasks for any non point-to-point network interfaces in the
479 system which are on the same network. (Note: on some platforms, pppd
480 will always use 255.255.255.255 for the netmask, if that is the only
481 appropriate value for a point-to-point interface.)
484 Disable Address/Control compression in both directions (send and
488 Do not require the peer to authenticate itself. This option is
492 Disables BSD-Compress compression; \fBpppd\fR will not request or
493 agree to compress packets using the BSD-Compress scheme.
496 Disable CCP (Compression Control Protocol) negotiation. This option
497 should only be required if the peer is buggy and gets confused by
498 requests from pppd for CCP negotiation.
501 Disable hardware flow control (i.e. RTS/CTS) on the serial port.
502 If neither the \fIcrtscts\fR nor the \fInocrtscts\fR nor the
503 \fIcdtrcts\fR nor the \fInodtrcts\fR option is given, the hardware
504 flow control setting for the serial port is left unchanged.
507 This option is a synonym for \fInocrtscts\fR. Either of these options will
508 disable both forms of hardware flow control.
511 Disable the \fIdefaultroute\fR option. The system administrator who
512 wishes to prevent users from creating default routes with pppd
513 can do so by placing this option in the /etc/ppp/options file.
516 Disables Deflate compression; pppd will not request or agree to
517 compress packets using the Deflate scheme.
520 Don't detach from the controlling terminal. Without this option, if a
521 serial device other than the terminal on the standard input is
522 specified, pppd will fork to become a background process.
525 Disable IPCP negotiation and IP communication. This option should
526 only be required if the peer is buggy and gets confused by requests
527 from pppd for IPCP negotiation.
530 Disables the default behaviour when no local IP address is specified,
531 which is to determine (if possible) the local IP address from the
532 hostname. With this option, the peer will have to supply the local IP
533 address during IPCP negotiation (unless it specified explicitly on the
534 command line or in an options file).
537 Disable the IPXCP and IPX protocols. This option should only be
538 required if the peer is buggy and gets confused by requests from pppd
539 for IPXCP negotiation.
542 Disable magic number negotiation. With this option, pppd cannot
543 detect a looped-back line. This option should only be needed if the
547 Disable protocol field compression negotiation in both the receive and
548 the transmit direction.
551 Exit once a connection has been made and terminated. This is the
552 default unless the \fIpersist\fR or \fIdemand\fR option has been
556 Do not accept or agree to Predictor-1 comprssion.
559 Disable the \fIproxyarp\fR option. The system administrator who
560 wishes to prevent users from creating proxy ARP entries with pppd can
561 do so by placing this option in the /etc/ppp/options file.
564 Normally, pppd requires a terminal device. With this option, pppd
565 will allocate itself a pseudo-tty master/slave pair and use the slave
566 as its terminal device. Pppd will create a child process to act as a
567 `character shunt' to transfer characters between the pseudo-tty master
568 and its standard input and output. Thus pppd will transmit characters
569 on its standard output and receive characters on its standard input
570 even if they are not terminal devices. This option increases the
571 latency and CPU overhead of transferring data over the ppp interface
572 as all of the characters sent and received must flow through the
573 character shunt process. An explicit device name may not be given if
577 Disable Van Jacobson style TCP/IP header compression in both the
578 transmit and the receive direction.
581 Disable the connection-ID compression option in Van Jacobson style
582 TCP/IP header compression. With this option, pppd will not omit the
583 connection-ID byte from Van Jacobson compressed TCP/IP headers, nor
584 ask the peer to do so.
587 Indicates that all secrets in the /etc/ppp/pap-secrets file which are
588 used for checking the identity of the peer are encrypted, and thus
589 pppd should not accept a password which, before encryption, is
590 identical to the secret from the /etc/ppp/pap-secrets file.
592 .B pap-max-authreq \fIn
593 Set the maximum number of PAP authenticate-request transmissions to
594 \fIn\fR (default 10).
597 Set the PAP restart interval (retransmission timeout) to \fIn\fR
601 Set the maximum time that pppd will wait for the peer to authenticate
602 itself with PAP to \fIn\fR seconds (0 means no limit).
604 .B pass-filter \fIfilter-expression
605 Specifies a packet filter to applied to data packets being sent or
606 received to determine which packets should be allowed to pass.
607 Packets which are rejected by the filter are silently discarded. This
608 option can be used to prevent specific network daemons (such as
609 routed) using up link bandwidth, or to provide a basic firewall
611 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
612 except that qualifiers which are inappropriate for a PPP link, such as
613 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
614 expression should be enclosed in single-quotes to prevent whitespace
615 in the expression from being interpreted by the shell. Note that it
616 is possible to apply different constraints to incoming and outgoing
617 packets using the \fBinbound\fR and \fBoutbound\fR qualifiers. This
618 option is currently only available under NetBSD, and then only if both
619 the kernel and pppd were compiled with PPP_FILTER defined.
622 Do not exit after a connection is terminated; instead try to reopen
626 Request that the peer compress frames that it sends using Predictor-1
627 compression, and agree to compress transmitted frames with Predictor-1
628 if requested. This option has no effect unless the kernel driver
629 supports Predictor-1 compression.
631 .B privgroup \fIgroup-name
632 Allows members of group \fIgroup-name\fR to use privileged options.
633 This is a privileged option. Use of this option requires care as
634 there is no guarantee that members of \fIgroup-name\fR cannot use pppd
635 to become root themselves. Consider it equivalent to putting the
636 members of \fIgroup-name\fR in the kmem or disk group.
639 Add an entry to this system's ARP [Address Resolution Protocol] table
640 with the IP address of the peer and the Ethernet address of this
641 system. This will have the effect of making the peer appear to other
642 systems to be on the local ethernet.
645 Specifies that the command \fIscript\fR is to be used to communicate
646 rather than a specific terminal device. Pppd will allocate itself a
647 pseudo-tty master/slave pair and use the slave as its terminal
648 device. The \fIscript\fR will be run in a child process with the
649 pseudo-tty master as its standard input and output. An explicit
650 device name may not be given if this option is used.
653 With this option, pppd will accept all control characters from the
654 peer, including those marked in the receive asyncmap. Without this
655 option, pppd will discard those characters as specified in RFC1662.
656 This option should only be needed if the peer is buggy.
658 .B record \fIfilename
659 Specifies that pppd should record all characters sent and received to
660 a file named \fIfilename\fR. This file is opened in append mode,
661 using the user's user-ID and permissions. This option is implemented
662 using a pseudo-tty and a process to transfer characters between the
663 pseudo-tty and the real serial device, so it will increase the latency
664 and CPU overhead of transferring data over the ppp interface. The
665 characters are stored in a tagged format with timestamps, which can be
666 displayed in readable form using the pppdump(8) program.
668 .B remotename \fIname
669 Set the assumed name of the remote system for authentication purposes
673 With this option, pppd will not agree to authenticate itself to the
677 With this option, pppd will not agree to authenticate itself to the
681 Require the peer to authenticate itself using CHAP [Challenge
682 Handshake Authentication Protocol] authentication.
685 Require the peer to authenticate itself using PAP [Password
686 Authentication Protocol] authentication.
689 With this option, pppd will not transmit LCP packets to initiate a
690 connection until a valid LCP packet is received from the peer (as for
691 the `passive' option with ancient versions of pppd).
694 Use synchronous HDLC serial encoding instead of asynchronous.
695 The device used by pppd with this option must support synchronous
696 serial communications. Currently supports Microgate SyncLink adapters
700 Enforce the use of the hostname (with domain name appended, if given)
701 as the name of the local system for authentication purposes (overrides
702 the \fIname\fR option). This option is not normally needed since the
703 \fIname\fR option is privileged.
706 Sets the name used for authenticating the local system to the peer to
710 Sets the number of connection slots to be used by the Van Jacobson
711 TCP/IP header compression and decompression code to \fIn\fR, which
712 must be between 2 and 16 (inclusive).
715 Run the executable or shell command specified by \fIscript\fR before
716 initiating PPP negotiation, after the connect script (if any) has
717 completed. A value for this option from a privileged source cannot be
718 overridden by a non-privileged user.
721 Use software flow control (i.e. XON/XOFF) to control the flow of data on
724 Options can be taken from files as well as the command line. Pppd
725 reads options from the files /etc/ppp/options, ~/.ppprc and
726 /etc/ppp/options.\fIttyname\fR (in that order) before processing the
727 options on the command line. (In fact, the command-line options are
728 scanned to find the terminal name before the options.\fIttyname\fR
729 file is read.) In forming the name of the options.\fIttyname\fR file,
730 the initial /dev/ is removed from the terminal name, and any remaining
731 / characters are replaced with dots.
733 An options file is parsed into a series of words, delimited by
734 whitespace. Whitespace can be included in a word by enclosing the
735 word in double-quotes ("). A backslash (\\) quotes the following character.
736 A hash (#) starts a comment, which continues until the end of the
737 line. There is no restriction on using the \fIfile\fR or \fIcall\fR
738 options within an options file.
741 provides system administrators with sufficient access control that PPP
742 access to a server machine can be provided to legitimate users without
743 fear of compromising the security of the server or the network it's
744 on. This control is provided through restrictions on which IP
745 addresses the peer may use, based on its authenticated identity (if
746 any), and through restrictions on which options a non-privileged user
747 may use. Several of pppd's options are privileged, in particular
748 those which permit potentially insecure configurations; these options
749 are only accepted in files which are under the control of the system
750 administrator, or if pppd is being run by root.
752 The default behaviour of pppd is to allow an unauthenticated peer to
753 use a given IP address only if the system does not already have a
754 route to that IP address. For example, a system with a
755 permanent connection to the wider internet will normally have a
756 default route, and thus all peers will have to authenticate themselves
757 in order to set up a connection. On such a system, the \fIauth\fR
758 option is the default. On the other hand, a system where the
759 PPP link is the only connection to the internet will not normally have
760 a default route, so the peer will be able to use almost any IP address
761 without authenticating itself.
763 As indicated above, some security-sensitive options are privileged,
764 which means that they may not be used by an ordinary non-privileged
765 user running a setuid-root pppd, either on the command line, in the
766 user's ~/.ppprc file, or in an options file read using the \fIfile\fR
767 option. Privileged options may be used in /etc/ppp/options file or in
768 an options file read using the \fIcall\fR option. If pppd is being
769 run by the root user, privileged options can be used without
772 When opening the device, pppd uses either the invoking user's user ID
773 or the root UID (that is, 0), depending on whether the device name was
774 specified by the user or the system administrator. If the device name
775 comes from a privileged source, that is, /etc/ppp/options or an
776 options file read using the \fIcall\fR option, pppd uses full root
777 privileges when opening the device. Thus, by creating an appropriate
778 file under /etc/ppp/peers, the system administrator can allow users to
779 establish a ppp connection via a device which they would not normally
780 have permission to access. Otherwise pppd uses the invoking user's
781 real UID when opening the device.
783 Authentication is the process whereby one peer convinces the other of
784 its identity. This involves the first peer sending its name to the
785 other, together with some kind of secret information which could only
786 come from the genuine authorized user of that name. In such an
787 exchange, we will call the first peer the "client" and the other the
788 "server". The client has a name by which it identifies itself to the
789 server, and the server also has a name by which it identifies itself
790 to the client. Generally the genuine client shares some secret (or
791 password) with the server, and authenticates itself by proving that it
792 knows that secret. Very often, the names used for authentication
793 correspond to the internet hostnames of the peers, but this is not
796 At present, pppd supports two authentication protocols: the Password
797 Authentication Protocol (PAP) and the Challenge Handshake
798 Authentication Protocol (CHAP). PAP involves the client sending its
799 name and a cleartext password to the server to authenticate itself.
800 In contrast, the server initiates the CHAP authentication exchange by
801 sending a challenge to the client (the challenge packet includes the
802 server's name). The client must respond with a response which
803 includes its name plus a hash value derived from the shared secret and
804 the challenge, in order to prove that it knows the secret.
806 The PPP protocol, being symmetrical, allows both peers to require the
807 other to authenticate itself. In that case, two separate and
808 independent authentication exchanges will occur. The two exchanges
809 could use different authentication protocols, and in principle,
810 different names could be used in the two exchanges.
812 The default behaviour of pppd is to agree to authenticate if
813 requested, and to not require authentication from the peer. However,
814 pppd will not agree to authenticate itself with a particular protocol
815 if it has no secrets which could be used to do so.
817 Pppd stores secrets for use in authentication in secrets
818 files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
819 Both secrets files have the same format. The secrets files can
820 contain secrets for pppd to use in authenticating itself to other
821 systems, as well as secrets for pppd to use when authenticating other
824 Each line in a secrets file contains one secret. A given secret is
825 specific to a particular combination of client and server - it can
826 only be used by that client to authenticate itself to that server.
827 Thus each line in a secrets file has at least 3 fields: the name of
828 the client, the name of the server, and the secret. These fields may
829 be followed by a list of the IP addresses that the specified client
830 may use when connecting to the specified server.
832 A secrets file is parsed into words as for a options file, so the
833 client name, server name and secrets fields must each be one word,
834 with any embedded spaces or other special characters quoted or
835 escaped. Any following words on the same line are taken to be a list
836 of acceptable IP addresses for that client. If there are only 3 words
837 on the line, or if the first word is "-", then all IP addresses are
838 disallowed. To allow any address, use "*".
839 A word starting with "!" indicates that the
840 specified address is \fInot\fR acceptable. An address may be followed
841 by "/" and a number \fIn\fR, to indicate a whole subnet, i.e. all
842 addresses which have the same value in the most significant \fIn\fR
843 bits. Note that case is significant in the client and server names
846 If the secret starts with an `@', what follows is assumed to be the
847 name of a file from which to read the secret. A "*" as the client or
848 server name matches any name. When selecting a secret, pppd takes the
849 best match, i.e. the match with the fewest wildcards.
851 Thus a secrets file contains both secrets for use in authenticating
852 other hosts, plus secrets which we use for authenticating ourselves to
853 others. When pppd is authenticating the peer (checking the peer's
854 identity), it chooses a secret with the peer's name in the first
855 field and the name of the local system in the second field. The
856 name of the local system defaults to the hostname, with the domain
857 name appended if the \fIdomain\fR option is used. This default can be
858 overridden with the \fIname\fR option, except when the
859 \fIusehostname\fR option is used.
861 When pppd is choosing a secret to use in authenticating itself to the
862 peer, it first determines what name it is going to use to identify
863 itself to the peer. This name can be specified by the user with the
864 \fIuser\fR option. If this option is not used, the name defaults to
865 the name of the local system, determined as described in the previous
866 paragraph. Then pppd looks for a secret with this name in the first
867 field and the peer's name in the second field. Pppd will know the
868 name of the peer if CHAP authentication is being used, because the
869 peer will have sent it in the challenge packet. However, if PAP is being
870 used, pppd will have to determine the peer's name from the options
871 specified by the user. The user can specify the peer's name directly
872 with the \fIremotename\fR option. Otherwise, if the remote IP address
873 was specified by a name (rather than in numeric form), that name will
874 be used as the peer's name. Failing that, pppd will use the null
875 string as the peer's name.
877 When authenticating the peer with PAP, the supplied password is first
878 compared with the secret from the secrets file. If the password
879 doesn't match the secret, the password is encrypted using crypt() and
880 checked against the secret again. Thus secrets for authenticating the
881 peer can be stored in encrypted form if desired. If the
882 \fIpapcrypt\fR option is given, the first (unencrypted) comparison is
883 omitted, for better security.
885 Furthermore, if the \fIlogin\fR option was specified, the username and
886 password are also checked against the system password database. Thus,
887 the system administrator can set up the pap-secrets file to allow PPP
888 access only to certain users, and to restrict the set of IP addresses
889 that each user can use. Typically, when using the \fIlogin\fR option,
890 the secret in /etc/ppp/pap-secrets would be "", which will match any
891 password supplied by the peer. This avoids the need to have the same
892 secret in two places.
894 Authentication must be satisfactorily completed before IPCP (or any
895 other Network Control Protocol) can be started. If the peer is
896 required to authenticate itself, and fails to do so, pppd will
897 terminated the link (by closing LCP). If IPCP negotiates an
898 unacceptable IP address for the remote host, IPCP will be closed. IP
899 packets can only be sent or received when IPCP is open.
901 In some cases it is desirable to allow some hosts which can't
902 authenticate themselves to connect and use one of a restricted set of
903 IP addresses, even when the local host generally requires
904 authentication. If the peer refuses to authenticate itself when
905 requested, pppd takes that as equivalent to authenticating with PAP
906 using the empty string for the username and password. Thus, by adding
907 a line to the pap-secrets file which specifies the empty string for
908 the client and password, it is possible to allow restricted access to
909 hosts which refuse to authenticate themselves.
912 When IPCP negotiation is completed successfully, pppd will inform the
913 kernel of the local and remote IP addresses for the ppp interface.
914 This is sufficient to create a host route to the remote end of the
915 link, which will enable the peers to exchange IP packets.
916 Communication with other machines generally requires further
917 modification to routing tables and/or ARP (Address Resolution
918 Protocol) tables. In most cases the \fIdefaultroute\fR and/or
919 \fIproxyarp\fR options are sufficient for this, but in some cases
920 further intervention is required. The /etc/ppp/ip-up script can be
923 Sometimes it is desirable to add a default route through the remote
924 host, as in the case of a machine whose only connection to the
925 Internet is through the ppp interface. The \fIdefaultroute\fR option
926 causes pppd to create such a default route when IPCP comes up, and
927 delete it when the link is terminated.
929 In some cases it is desirable to use proxy ARP, for example on a
930 server machine connected to a LAN, in order to allow other hosts to
931 communicate with the remote host. The \fIproxyarp\fR option causes
932 pppd to look for a network interface on the same subnet as the remote
933 host (an interface supporting broadcast and ARP, which is up and not a
934 point-to-point or loopback interface). If found, pppd creates a
935 permanent, published ARP entry with the IP address of the remote host
936 and the hardware address of the network interface found.
938 When the \fIdemand\fR option is used, the interface IP addresses have
939 already been set at the point when IPCP comes up. If pppd has not
940 been able to negotiate the same addresses that it used to configure
941 the interface (for example when the peer is an ISP that uses dynamic
942 IP address assignment), pppd has to change the interface IP addresses
943 to the negotiated addresses. This may disrupt existing connections,
944 and the use of demand dialling with peers that do dynamic IP address
945 assignment is not recommended.
948 The following examples assume that the /etc/ppp/options file contains
949 the \fIauth\fR option (as in the default /etc/ppp/options file in the
952 Probably the most common use of pppd is to dial out to an ISP. This
953 can be done with a command such as
957 where the /etc/ppp/peers/isp file is set up by the system
958 administrator to contain something like this:
962 connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
966 In this example, we are using chat to dial the ISP's modem and go
967 through any logon sequence required. The /etc/ppp/chat-isp file
968 contains the script used by chat; it could for example contain
981 ABORT "Username/Password Incorrect"
991 "word:" "\\qmypassword"
997 See the chat(8) man page for details of chat scripts.
999 Pppd can also be used to provide a dial-in ppp service for users. If
1000 the users already have login accounts, the simplest way to set up the
1001 ppp service is to let the users log in to their accounts and run pppd
1002 (installed setuid-root) with a command such as
1006 To allow a user to use the PPP facilities, you need to allocate an IP
1007 address for that user's machine and create an entry in
1008 /etc/ppp/pap-secrets or /etc/ppp/chap-secrets (depending on which
1009 authentication method the PPP implementation on the user's machine
1010 supports), so that the user's
1011 machine can authenticate itself. For example, if Joe has a machine
1012 called "joespc" which is to be allowed to dial in to the machine
1013 called "server" and use the IP address joespc.my.net, you would add an
1014 entry like this to /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:
1016 joespc server "joe's secret" joespc.my.net
1018 Alternatively, you can create a username called (for example) "ppp",
1019 whose login shell is pppd and whose home directory is /etc/ppp.
1020 Options to be used when pppd is run this way can be put in
1023 If your serial connection is any more complicated than a piece of
1024 wire, you may need to arrange for some control characters to be
1025 escaped. In particular, it is often useful to escape XON (^Q) and
1026 XOFF (^S), using \fIasyncmap a0000\fR. If the path includes a telnet,
1027 you probably should escape ^] as well (\fIasyncmap 200a0000\fR). If
1028 the path includes an rlogin, you will need to use the \fIescape ff\fR
1029 option on the end which is running the rlogin client, since many
1030 rlogin implementations are not transparent; they will remove the
1031 sequence [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the
1035 Messages are sent to the syslog daemon using facility LOG_DAEMON.
1036 (This can be overriden by recompiling pppd with the macro
1037 LOG_PPP defined as the desired facility.) In order to see the error
1038 and debug messages, you will need to edit your /etc/syslog.conf file
1039 to direct the messages to the desired output device or file.
1041 The \fIdebug\fR option causes the contents of all control packets sent
1042 or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
1043 This can be useful if the PPP negotiation does not succeed or if
1044 authentication fails.
1045 If debugging is enabled at compile time, the \fIdebug\fR option also
1046 causes other debugging messages to be logged.
1048 Debugging can also be enabled or disabled by sending a SIGUSR1 signal
1049 to the pppd process. This signal acts as a toggle.
1051 Pppd invokes scripts at various stages in its processing which can be
1052 used to perform site-specific ancillary processing. These scripts are
1053 usually shell scripts, but could be executable code files instead.
1054 Pppd does not wait for the scripts to finish. The scripts are
1055 executed as root (with the real and effective user-id set to 0), so
1056 that they can do things such as update routing tables or run
1057 privileged daemons. Be careful that the contents of these scripts do
1058 not compromise your system's security. Pppd runs the scripts with
1059 standard input, output and error redirected to /dev/null, and with an
1060 environment that is empty except for some environment variables that
1061 give information about the link. The environment variables that pppd
1065 The name of the serial tty device being used.
1068 The name of the network interface being used.
1071 The IP address for the local end of the link. This is only set when
1075 The IP address for the remote end of the link. This is only set when
1079 The authenticated name of the peer. This is only set if the peer
1080 authenticates itself.
1082 The baud rate of the tty device.
1085 The real user-id of the user who invoked pppd.
1087 The username of the real user-id that invoked pppd. This is always set.
1090 Pppd invokes the following scripts, if they exist. It is not an error
1091 if they don't exist.
1094 A program or script which is executed after the remote system
1095 successfully authenticates itself. It is executed with the parameters
1097 \fIinterface-name peer-name user-name tty-device speed\fR
1099 Note that this script is not executed if the peer doesn't authenticate
1100 itself, for example when the \fInoauth\fR option is used.
1102 .B /etc/ppp/auth-down
1103 A program or script which is executed when the link goes down, if
1104 /etc/ppp/auth-up was previously executed. It is executed in the same
1105 manner with the same parameters as /etc/ppp/auth-up.
1108 A program or script which is executed when the link is available for
1109 sending and receiving IP packets (that is, IPCP has come up). It is
1110 executed with the parameters
1112 \fIinterface-name tty-device speed local-IP-address
1113 remote-IP-address ipparam\fR
1116 A program or script which is executed when the link is no longer
1117 available for sending and receiving IP packets. This script can be
1118 used for undoing the effects of the /etc/ppp/ip-up script. It is
1119 invoked in the same manner and with the same parameters as the ip-up
1123 A program or script which is executed when the link is available for
1124 sending and receiving IPX packets (that is, IPXCP has come up). It is
1125 executed with the parameters
1127 \fIinterface-name tty-device speed network-number local-IPX-node-address
1128 remote-IPX-node-address local-IPX-routing-protocol remote-IPX-routing-protocol
1129 local-IPX-router-name remote-IPX-router-name ipparam pppd-pid\fR
1131 The local-IPX-routing-protocol and remote-IPX-routing-protocol field
1132 may be one of the following:
1134 NONE to indicate that there is no routing protocol
1136 RIP to indicate that RIP/SAP should be used
1138 NLSP to indicate that Novell NLSP should be used
1140 RIP NLSP to indicate that both RIP/SAP and NLSP should be used
1142 .B /etc/ppp/ipx-down
1143 A program or script which is executed when the link is no longer
1144 available for sending and receiving IPX packets. This script can be
1145 used for undoing the effects of the /etc/ppp/ipx-up script. It is
1146 invoked in the same manner and with the same parameters as the ipx-up
1150 .B /var/run/ppp\fIn\fB.pid \fR(BSD or Linux), \fB/etc/ppp/ppp\fIn\fB.pid \fR(others)
1151 Process-ID for pppd process on ppp interface unit \fIn\fR.
1153 .B /etc/ppp/pap-secrets
1154 Usernames, passwords and IP addresses for PAP authentication. This
1155 file should be owned by root and not readable or writable by any other
1156 user. Pppd will log a warning if this is not the case.
1158 .B /etc/ppp/chap-secrets
1159 Names, secrets and IP addresses for CHAP authentication. As for
1160 /etc/ppp/pap-secrets, this file should be owned by root and not
1161 readable or writable by any other user. Pppd will log a warning if
1162 this is not the case.
1165 System default options for pppd, read before user default options or
1166 command-line options.
1169 User default options, read before /etc/ppp/options.\fIttyname\fR.
1171 .B /etc/ppp/options.\fIttyname
1172 System default options for the serial port being used, read after
1173 ~/.ppprc. In forming the \fIttyname\fR part of this
1174 filename, an initial /dev/ is stripped from the port name (if
1175 present), and any slashes in the remaining part are converted to
1179 A directory containing options files which may contain privileged
1180 options, even if pppd was invoked by a user other than root. The
1181 system administrator can create options files in this directory to
1182 permit non-privileged users to dial out without requiring the peer to
1183 authenticate, but only to certain trusted peers.
1188 \fICompressing TCP/IP headers for low-speed serial links.\fR
1193 .I The MD5 Message-Digest Algorithm.
1198 .I PPP Internet Protocol Control Protocol (IPCP).
1202 Lloyd, B.; Simpson, W.A.
1203 .I PPP authentication protocols.
1208 .I The Point\-to\-Point Protocol (PPP).
1213 .I PPP in HDLC-like Framing.
1216 The following signals have the specified effect when sent to pppd.
1219 These signals cause pppd to terminate the link (by closing LCP),
1220 restore the serial device settings, and exit.
1223 This signal causes pppd to terminate the link, restore the serial
1224 device settings, and close the serial device. If the \fIpersist\fR or
1225 \fIdemand\fR option has been specified, pppd will try to reopen the
1226 serial device and start another connection (after the holdoff period).
1227 Otherwise pppd will exit. If this signal is received during the
1228 holdoff period, it causes pppd to end the holdoff period immediately.
1231 This signal toggles the state of the \fIdebug\fR option.
1234 This signal causes pppd to renegotiate compression. This can be
1235 useful to re-enable compression after it has been disabled as a result
1236 of a fatal decompression error. (Fatal decompression errors generally
1237 indicate a bug in one or other implementation.)
1240 Paul Mackerras (Paul.Mackerras@cs.anu.edu.au), based on earlier work by
projects / ppp.git / blob