1 .\" manual page [] for pppd 2.3
2 .\" $Id: pppd.8,v 1.28 1998/09/04 18:49:15 christos 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
39 will use that terminal, and will not fork to put itself in the
40 background. This option is privileged if the \fInoauth\fR option is
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.
48 .B active-filter \fIfilter-expression
49 Specifies a packet filter to be applied to data packets to determine
50 which packets are to be regarded as link activity, and therefore reset
51 the idle timer, or cause the link to be brought up in demand-dialling
52 mode. This option is useful in conjunction with the
53 \fBidle\fR option if there are packets being sent or received
54 regularly over the link (for example, routing information packets)
55 which would otherwise prevent the link from ever appearing to be idle.
56 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
57 except that qualifiers which are inappropriate for a PPP link, such as
58 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
59 expression should be enclosed in single-quotes to prevent whitespace
60 in the expression from being interpreted by the shell. This option
61 is currently only available under NetBSD, and then only
62 if both the kernel and pppd were compiled with PPP_FILTER defined.
65 Set the async character map to <map>. This map describes which
66 control characters cannot be successfully received over the serial
67 line. Pppd will ask the peer to send these characters as a 2-byte
68 escape sequence. The argument is a 32 bit hex number with each bit
69 representing a character to escape. Bit 0 (00000001) represents the
70 character 0x00; bit 31 (80000000) represents the character 0x1f or ^_.
71 If multiple \fIasyncmap\fR options are given, the values are ORed
72 together. If no \fIasyncmap\fR option is given, no async character
73 map will be negotiated for the receive direction; the peer should then
74 escape \fIall\fR control characters. To escape transmitted
75 characters, use the \fIescape\fR option.
78 Require the peer to authenticate itself before allowing network
79 packets to be sent or received.
82 Read options from the file /etc/ppp/peers/\fIname\fR. This file may
83 contain privileged options, such as \fInoauth\fR, even if pppd
84 is not being run by root. The \fIname\fR string may not begin with /
85 or include .. as a pathname component. The format of the options file
89 Use the executable or shell command specified by \fIscript\fR to set
90 up the serial line. This script would typically use the chat(8)
91 program to dial the modem and start the remote ppp session. This
92 option is privileged if the \fInoauth\fR option is used.
95 Use hardware flow control (i.e. RTS/CTS) to control the flow of
96 data on the serial port. If neither the \fIcrtscts\fR, the
97 \fInocrtscts\fR, the \fIcdtrcts\fR nor the \fInocdtrcts\fR option
98 is given, the hardware flow control setting for the serial port is
100 Some serial ports (such as Macintosh serial ports) lack a true
101 RTS output. Such serial ports use this mode to impliment
102 unidirectional flow control. The serial port will
103 suspend transmission when requested by the modem (via CTS)
104 but will be unable to request the modem stop sending to the
105 computer. This mode retains the ability to use DTR as
106 a modem control line.
109 Use a non-standard hardware flow control (i.e. DTR/CTS) to control
110 the flow of data on the serial port. If neither the \fIcrtscts\fR,
111 the \fInocrtscts\fR, the \fIcdtrcts\fR nor the \fInocdtrcts\fR
112 option is given, the hardware flow control setting for the serial
113 port is left unchanged.
114 Some serial ports (such as Macintosh serial ports) lack a true
115 RTS output. Such serial ports use this mode to impliment true
116 bi-directional flow control. The sacrafice is that this flow
117 control mode does not permit using DTR as a modem control line.
120 Add a default route to the system routing tables, using the peer as
121 the gateway, when IPCP negotiation is successfully completed.
122 This entry is removed when the PPP connection is broken. This option
123 is privileged if the \fInodefaultroute\fR option has been specified.
125 .B disconnect \fIscript
126 Run the executable or shell command specified by \fIscript\fR after
127 pppd has terminated the link. This script could, for example, issue
128 commands to the modem to cause it to hang up if hardware modem control
129 signals were not available. The disconnect script is not run if the
130 modem has already hung up. This option is privileged if the
131 \fInoauth\fR option is used.
133 .B escape \fIxx,yy,...
134 Specifies that certain characters should be escaped on transmission
135 (regardless of whether the peer requests them to be escaped with its
136 async control character map). The characters to be escaped are
137 specified as a list of hex numbers separated by commas. Note that
138 almost any character can be specified for the \fIescape\fR option,
139 unlike the \fIasyncmap\fR option which only allows control characters
140 to be specified. The characters which may not be escaped are those
141 with hex values 0x20 - 0x3f or 0x5e.
144 Read options from file \fIname\fR (the format is described below).
145 The file must be readable by the user who has invoked pppd.
148 Specifies that pppd should create a UUCP-style lock file for the
149 serial device to ensure exclusive access to the device.
152 Set the MRU [Maximum Receive Unit] value to \fIn\fR. Pppd
153 will ask the peer to send packets of no more than \fIn\fR bytes. The
154 minimum MRU value is 128. The default MRU value is 1500. A value of
155 296 is recommended for slow links (40 bytes for TCP/IP header + 256
159 Set the MTU [Maximum Transmit Unit] value to \fIn\fR. Unless the
160 peer requests a smaller value via MRU negotiation, pppd will
161 request that the kernel networking code send data packets of no more
162 than \fIn\fR bytes through the PPP network interface.
165 Enables the "passive" option in the LCP. With this option, pppd will
166 attempt to initiate a connection; if no reply is received from the
167 peer, pppd will then just wait passively for a valid LCP packet from
168 the peer, instead of exiting, as it would without this option.
171 .I <local_IP_address>\fB:\fI<remote_IP_address>
172 Set the local and/or remote interface IP addresses. Either one may be
173 omitted. The IP addresses can be specified with a host name or in
174 decimal dot notation (e.g. 150.234.56.78). The default local
175 address is the (first) IP address of the system (unless the
177 option is given). The remote address will be obtained from the peer
178 if not specified in any option. Thus, in simple cases, this option is
179 not required. If a local and/or remote IP address is specified with
181 will not accept a different value from the peer in the IPCP
182 negotiation, unless the \fIipcp-accept-local\fR and/or
183 \fIipcp-accept-remote\fR options are given, respectively.
186 Request that the peer compress packets that it sends, using the
187 BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
188 agree to compress packets sent to the peer with a maximum code size of
189 \fInt\fR bits. If \fInt\fR is not specified, it defaults to the value
190 given for \fInr\fR. Values in the range 9 to 15 may be used for
191 \fInr\fR and \fInt\fR; larger values give better compression but
192 consume more kernel memory for compression dictionaries.
193 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
194 compression in the corresponding direction. Use \fInobsdcomp\fR or
195 \fIbsdcomp 0\fR to disable BSD-Compress compression entirely.
197 .B chap-interval \fIn
198 If this option is given, pppd will rechallenge the peer every \fIn\fR
201 .B chap-max-challenge \fIn
202 Set the maximum number of CHAP challenge transmissions to \fIn\fR
206 Set the CHAP restart interval (retransmission timeout for challenges)
207 to \fIn\fR seconds (default 3).
210 Enables connection debugging facilities.
211 If this option is given, pppd will log the contents of all
212 control packets sent or received in a readable form. The packets are
213 logged through syslog with facility \fIdaemon\fR and level
214 \fIdebug\fR. This information can be directed to a file by setting up
215 /etc/syslog.conf appropriately (see syslog.conf(5)).
218 Disable asyncmap negotiation, forcing all control characters to be
219 escaped for both the transmit and the receive direction.
222 Disable MRU [Maximum Receive Unit] negotiation. With this option,
223 pppd will use the default MRU value of 1500 bytes for both the
224 transmit and receive direction.
227 Request that the peer compress packets that it sends, using the
228 Deflate scheme, with a maximum window size of \fI2**nr\fR bytes, and
229 agree to compress packets sent to the peer with a maximum window size
230 of \fI2**nt\fR bytes. If \fInt\fR is not specified, it defaults to
231 the value given for \fInr\fR. Values in the range 8 to 15 may be used
232 for \fInr\fR and \fInt\fR; larger values give better compression but
233 consume more kernel memory for compression dictionaries.
234 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
235 compression in the corresponding direction. Use \fInodeflate\fR or
236 \fIdeflate 0\fR to disable Deflate compression entirely. (Note: pppd
237 requests Deflate compression in preference to BSD-Compress if the peer
241 Initiate the link only on demand, i.e. when data traffic is present.
242 With this option, the remote IP address must be specified by the user
243 on the command line or in an options file. Pppd will initially
244 configure the interface and enable it for IP traffic without
245 connecting to the peer. When traffic is available, pppd will
246 connect to the peer and perform negotiation, authentication, etc.
247 When this is completed, pppd will commence passing data packets
248 (i.e., IP packets) across the link.
250 The \fIdemand\fR option implies the \fIpersist\fR option. If this
251 behaviour is not desired, use the \fInopersist\fR option after the
252 \fIdemand\fR option. The \fIidle\fR and \fIholdoff\fR
253 options are also useful in conjuction with the \fIdemand\fR option.
256 Append the domain name \fId\fR to the local host name for authentication
257 purposes. For example, if gethostname() returns the name porsche, but
258 the fully qualified domain name is porsche.Quotron.COM, you could
259 specify \fIdomain Quotron.COM\fR. Pppd would then use the name
260 \fIporsche.Quotron.COM\fR for looking up secrets in the secrets file,
261 and as the default name to send to the peer when authenticating itself
262 to the peer. This option is privileged.
265 Specifies how many seconds to wait before re-initiating the link after
266 it terminates. This option only has any effect if the \fIpersist\fR
267 or \fIdemand\fR option is used. The holdoff period is not applied if
268 the link was terminated because it was idle.
271 Specifies that pppd should disconnect if the link is idle for \fIn\fR
272 seconds. The link is idle when no data packets (i.e. IP packets) are
273 being sent or received. Note: it is not advisable to use this option
274 with the \fIpersist\fR option without the \fIdemand\fR option.
275 If the \fBactive-filter\fR
276 option is given, data packets which are rejected by the specified
277 activity filter also count as the link being idle.
280 With this option, pppd will accept the peer's idea of our local IP
281 address, even if the local IP address was specified in an option.
283 .B ipcp-accept-remote
284 With this option, pppd will accept the peer's idea of its (remote) IP
285 address, even if the remote IP address was specified in an option.
287 .B ipcp-max-configure \fIn
288 Set the maximum number of IPCP configure-request transmissions to
289 \fIn\fR (default 10).
291 .B ipcp-max-failure \fIn
292 Set the maximum number of IPCP configure-NAKs returned before starting
293 to send configure-Rejects instead to \fIn\fR (default 10).
295 .B ipcp-max-terminate \fIn
296 Set the maximum number of IPCP terminate-request transmissions to
300 Set the IPCP restart interval (retransmission timeout) to \fIn\fR
304 Provides an extra parameter to the ip-up and ip-down scripts. If this
305 option is given, the \fIstring\fR supplied is given as the 6th
306 parameter to those scripts.
309 Enable the IPXCP and IPX protocols. This option is presently only
310 supported under Linux, and only if your kernel has been configured to
314 Set the IPX network number in the IPXCP configure request frame to
315 \fIn\fR, a hexadecimal number (without a leading 0x). There is no
316 valid default. If this option is not specified, the network number is
317 obtained from the peer. If the peer does not have the network number,
318 the IPX protocol will not be started.
320 .B ipx-node \fIn\fB:\fIm
321 Set the IPX node numbers. The two node numbers are separated from each
322 other with a colon character. The first number \fIn\fR is the local
323 node number. The second number \fIm\fR is the peer's node number. Each
324 node number is a hexadecimal number, at most 10 digits long. The node
325 numbers on the ipx-network must be unique. There is no valid
326 default. If this option is not specified then the node numbers are
327 obtained from the peer.
329 .B ipx-router-name \fI<string>
330 Set the name of the router. This is a string and is sent to the peer
334 Set the routing protocol to be received by this option. More than one
335 instance of \fIipx-routing\fR may be specified. The '\fInone\fR'
336 option (0) may be specified as the only instance of ipx-routing. The
337 values may be \fI0\fR for \fINONE\fR, \fI2\fR for \fIRIP/SAP\fR, and
338 \fI4\fR for \fINLSP\fR.
340 .B ipxcp-accept-local
341 Accept the peer's NAK for the node number specified in the ipx-node
342 option. If a node number was specified, and non-zero, the default is
343 to insist that the value be used. If you include this option then you
344 will permit the peer to override the entry of the node number.
346 .B ipxcp-accept-network
347 Accept the peer's NAK for the network number specified in the
348 ipx-network option. If a network number was specified, and non-zero, the
349 default is to insist that the value be used. If you include this
350 option then you will permit the peer to override the entry of the node
353 .B ipxcp-accept-remote
354 Use the peer's network number specified in the configure request
355 frame. If a node number was specified for the peer and this option was
356 not specified, the peer will be forced to use the value which you have
359 .B ipxcp-max-configure \fIn
360 Set the maximum number of IPXCP configure request frames which the
361 system will send to \fIn\fR. The default is 10.
363 .B ipxcp-max-failure \fIn
364 Set the maximum number of IPXCP NAK frames which the local system will
365 send before it rejects the options. The default value is 3.
367 .B ipxcp-max-terminate \fIn
368 Set the maximum nuber of IPXCP terminate request frames before the
369 local system considers that the peer is not listening to them. The
373 Enable debugging code in the kernel-level PPP driver. The argument
374 \fIn\fR is a number which is the sum of the following values: 1 to
375 enable general debug messages, 2 to request that the contents of
376 received packets be printed, and 4 to request that the contents of
377 transmitted packets be printed. On most systems, messages printed by
378 the kernel are logged by syslog(1) to a file as directed in the
379 /etc/syslog.conf configuration file.
381 .B lcp-echo-failure \fIn
382 If this option is given, pppd will presume the peer to be dead
383 if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
384 echo-reply. If this happens, pppd will terminate the
385 connection. Use of this option requires a non-zero value for the
386 \fIlcp-echo-interval\fR parameter. This option can be used to enable
387 pppd to terminate after the physical connection has been broken
388 (e.g., the modem has hung up) in situations where no hardware modem
389 control lines are available.
391 .B lcp-echo-interval \fIn
392 If this option is given, pppd will send an LCP echo-request frame to
393 the peer every \fIn\fR seconds. Normally the peer should respond to
394 the echo-request by sending an echo-reply. This option can be used
395 with the \fIlcp-echo-failure\fR option to detect that the peer is no
398 .B lcp-max-configure \fIn
399 Set the maximum number of LCP configure-request transmissions to
400 \fIn\fR (default 10).
402 .B lcp-max-failure \fIn
403 Set the maximum number of LCP configure-NAKs returned before starting
404 to send configure-Rejects instead to \fIn\fR (default 10).
406 .B lcp-max-terminate \fIn
407 Set the maximum number of LCP terminate-request transmissions to
411 Set the LCP restart interval (retransmission timeout) to \fIn\fR
415 Don't use the modem control lines. With this option, pppd will ignore
416 the state of the CD (Carrier Detect) signal from the modem and will
417 not change the state of the DTR (Data Terminal Ready) signal.
420 Use the system password database for authenticating the peer using
421 PAP, and record the user in the system wtmp file. Note that the peer
422 must have an entry in the /etc/ppp/pap-secrets file as well as the
423 system password database to be allowed access.
426 Terminate the connection when it has been available for network
427 traffic for \fIn\fR seconds (i.e. \fIn\fR seconds after the first
428 network control protocol comes up).
431 Use the modem control lines. This option is the default. With this
432 option, pppd will wait for the CD (Carrier Detect) signal from the
433 modem to be asserted when opening the serial device (unless a connect
434 script is specified), and it will drop the DTR (Data Terminal Ready)
435 signal briefly when the connection is terminated and before executing
436 the connect script. On Ultrix, this option implies hardware flow
437 control, as for the \fIcrtscts\fR option.
440 If pppd is acting as a server for Microsoft Windows clients, this
441 option allows pppd to supply one or two DNS (Domain Name Server)
442 addresses to the clients. The first instance of this option specifies
443 the primary DNS address; the second instance (if given) specifies the
444 secondary DNS address. (This option was present in some older
445 versions of pppd under the name \fBdns-addr\fR.)
448 If pppd is acting as a server for Microsoft Windows or "Samba"
449 clients, this option allows pppd to supply one or two WINS (Windows
450 Internet Name Services) server addresses to the clients. The first
451 instance of this option specifies the primary WINS address; the second
452 instance (if given) specifies the secondary WINS address.
455 Set the name of the local system for authentication purposes to
456 \fIname\fR. This is a privileged option. With this option, pppd will
457 use lines in the secrets files which have \fIname\fR as the second
458 field when looking for a secret to use in authenticating the peer. In
459 addition, unless overridden with the \fIuser\fR option, \fIname\fR
460 will be used as the name to send to the peer when authenticating the
461 local system to the peer. (Note that pppd does not append the domain
465 Set the interface netmask to \fIn\fR, a 32 bit netmask in "decimal dot"
466 notation (e.g. 255.255.255.0). If this option is given, the value
467 specified is ORed with the default netmask. The default netmask is
468 chosen based on the negotiated remote IP address; it is the
469 appropriate network mask for the class of the remote IP address, ORed
470 with the netmasks for any non point-to-point network interfaces in the
471 system which are on the same network.
474 Disable Address/Control compression in both directions (send and
478 Do not require the peer to authenticate itself. This option is
479 privileged if the \fIauth\fR option is specified in /etc/ppp/options.
482 Disables BSD-Compress compression; \fBpppd\fR will not request or
483 agree to compress packets using the BSD-Compress scheme.
486 Disable CCP (Compression Control Protocol) negotiation. This option
487 should only be required if the peer is buggy and gets confused by
488 requests from pppd for CCP negotiation.
491 Disable hardware flow control (i.e. RTS/CTS) on the serial port.
492 If neither the \fIcrtscts\fR nor the \fInocrtscts\fR nor the
493 \fIcdtrcts\fR nor the \fInodtrcts\fR option is given, the hardware
494 flow control setting for the serial port is left unchanged.
497 This option is a synonym for \fInocrtscts\fR. Either of these options will
498 disable both forms of hardware flow control.
501 Disable the \fIdefaultroute\fR option. The system administrator who
502 wishes to prevent users from creating default routes with pppd
503 can do so by placing this option in the /etc/ppp/options file.
506 Disables Deflate compression; pppd will not request or agree to
507 compress packets using the Deflate scheme.
510 Don't detach from the controlling terminal. Without this option, if a
511 serial device other than the terminal on the standard input is
512 specified, pppd will fork to become a background process.
515 Disable IPCP negotiation and IP communication. This option should
516 only be required if the peer is buggy and gets confused by requests
517 from pppd for IPCP negotiation.
520 Disables the default behaviour when no local IP address is specified,
521 which is to determine (if possible) the local IP address from the
522 hostname. With this option, the peer will have to supply the local IP
523 address during IPCP negotiation (unless it specified explicitly on the
524 command line or in an options file).
527 Disable the IPXCP and IPX protocols. This option should only be
528 required if the peer is buggy and gets confused by requests from pppd
529 for IPXCP negotiation.
532 Disable magic number negotiation. With this option, pppd cannot
533 detect a looped-back line. This option should only be needed if the
537 Disable protocol field compression negotiation in both the receive and
538 the transmit direction.
541 Exit once a connection has been made and terminated. This is the
542 default unless the \fIpersist\fR or \fIdemand\fR option has been
546 Do not accept or agree to Predictor-1 comprssion.
549 Disable the \fIproxyarp\fR option. The system administrator who
550 wishes to prevent users from creating proxy ARP entries with pppd can
551 do so by placing this option in the /etc/ppp/options file.
554 Disable Van Jacobson style TCP/IP header compression in both the
555 transmit and the receive direction.
558 Disable the connection-ID compression option in Van Jacobson style
559 TCP/IP header compression. With this option, pppd will not omit the
560 connection-ID byte from Van Jacobson compressed TCP/IP headers, nor
561 ask the peer to do so.
564 Indicates that all secrets in the /etc/ppp/pap-secrets file which are
565 used for checking the identity of the peer are encrypted, and thus
566 pppd should not accept a password which, before encryption, is
567 identical to the secret from the /etc/ppp/pap-secrets file.
569 .B pap-max-authreq \fIn
570 Set the maximum number of PAP authenticate-request transmissions to
571 \fIn\fR (default 10).
574 Set the PAP restart interval (retransmission timeout) to \fIn\fR
578 Set the maximum time that pppd will wait for the peer to authenticate
579 itself with PAP to \fIn\fR seconds (0 means no limit).
581 .B pass-filter \fIfilter-expression
582 Specifies a packet filter to applied to data packets being sent or
583 received to determine which packets should be allowed to pass.
584 Packets which are rejected by the filter are silently discarded. This
585 option can be used to prevent specific network daemons (such as
586 routed) using up link bandwidth, or to provide a basic firewall
588 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
589 except that qualifiers which are inappropriate for a PPP link, such as
590 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
591 expression should be enclosed in single-quotes to prevent whitespace
592 in the expression from being interpreted by the shell. Note that it
593 is possible to apply different constraints to incoming and outgoing
594 packets using the \fBinbound\fR and \fBoutbound\fR qualifiers. This
595 option is currently only available under NetBSD, and then only if both
596 the kernel and pppd were compiled with PPP_FILTER defined.
599 Do not exit after a connection is terminated; instead try to reopen
603 Request that the peer compress frames that it sends using Predictor-1
604 compression, and agree to compress transmitted frames with Predictor-1
605 if requested. This option has no effect unless the kernel driver
606 supports Predictor-1 compression.
609 Add an entry to this system's ARP [Address Resolution Protocol] table
610 with the IP address of the peer and the Ethernet address of this
611 system. This will have the effect of making the peer appear to other
612 systems to be on the local ethernet.
614 .B remotename \fIname
615 Set the assumed name of the remote system for authentication purposes
619 With this option, pppd will not agree to authenticate itself to the
623 With this option, pppd will not agree to authenticate itself to the
627 Require the peer to authenticate itself using CHAP [Challenge
628 Handshake Authentication Protocol] authentication.
631 Require the peer to authenticate itself using PAP [Password
632 Authentication Protocol] authentication.
635 With this option, pppd will not transmit LCP packets to initiate a
636 connection until a valid LCP packet is received from the peer (as for
637 the `passive' option with ancient versions of pppd).
640 Enforce the use of the hostname (with domain name appended, if given)
641 as the name of the local system for authentication purposes (overrides
642 the \fIname\fR option).
645 Sets the name used for authenticating the local system to the peer to
649 Sets the number of connection slots to be used by the Van Jacobson
650 TCP/IP header compression and decompression code to \fIn\fR, which
651 must be between 2 and 16 (inclusive).
654 Run the executable or shell command specified by \fIscript\fR before
655 initiating PPP negotiation, after the connect script (if any) has
656 completed. This option is privileged if the \fInoauth\fR option is
660 Use software flow control (i.e. XON/XOFF) to control the flow of data on
663 Options can be taken from files as well as the command line. Pppd
664 reads options from the files /etc/ppp/options, ~/.ppprc and
665 /etc/ppp/options.\fIttyname\fR (in that order) before processing the
666 options on the command line. (In fact, the command-line options are
667 scanned to find the terminal name before the options.\fIttyname\fR
668 file is read.) In forming the name of the options.\fIttyname\fR file,
669 the initial /dev/ is removed from the terminal name, and any remaining
670 / characters are replaced with dots.
672 An options file is parsed into a series of words, delimited by
673 whitespace. Whitespace can be included in a word by enclosing the
674 word in double-quotes ("). A backslash (\\) quotes the following character.
675 A hash (#) starts a comment, which continues until the end of the
676 line. There is no restriction on using the \fIfile\fR or \fIcall\fR
677 options within an options file.
680 provides system administrators with sufficient access control that PPP
681 access to a server machine can be provided to legitimate users without
682 fear of compromising the security of the server or the network it's
683 on. In part this is provided by the /etc/ppp/options file, where the
684 administrator can place options to restrict the ways in which pppd can
685 be used, and in part by the PAP and CHAP secrets files, where the
686 administrator can restrict the set of IP addresses which individual
689 The normal way that pppd should be set up is to have the \fIauth\fR
690 option in the /etc/ppp/options file. (This may become the default in
691 later releases.) If users wish to use pppd to dial out to a peer
692 which will refuse to authenticate itself (such as an internet service
693 provider), the system administrator should create an options file
694 under /etc/ppp/peers containing the \fInoauth\fR option, the name of
695 the serial port to use, and the \fIconnect\fR option (if required),
696 plus any other appropriate options. In this way, pppd can be set up
697 to allow non-privileged users to make unauthenticated connections only
700 As indicated above, some security-sensitive options are privileged,
701 which means that they may not be used by an ordinary non-privileged
702 user running a setuid-root pppd, either on the command line, in the
703 user's ~/.ppprc file, or in an options file read using the \fIfile\fR
704 option. Privileged options may be used in /etc/ppp/options file or in
705 an options file read using the \fIcall\fR option. If pppd is being
706 run by the root user, privileged options can be used without
709 Authentication is the process whereby one peer convinces the other of
710 its identity. This involves the first peer sending its name to the
711 other, together with some kind of secret information which could only
712 come from the genuine authorized user of that name. In such an
713 exchange, we will call the first peer the "client" and the other the
714 "server". The client has a name by which it identifies itself to the
715 server, and the server also has a name by which it identifies itself
716 to the client. Generally the genuine client shares some secret (or
717 password) with the server, and authenticates itself by proving that it
718 knows that secret. Very often, the names used for authentication
719 correspond to the internet hostnames of the peers, but this is not
722 At present, pppd supports two authentication protocols: the Password
723 Authentication Protocol (PAP) and the Challenge Handshake
724 Authentication Protocol (CHAP). PAP involves the client sending its
725 name and a cleartext password to the server to authenticate itself.
726 In contrast, the server initiates the CHAP authentication exchange by
727 sending a challenge to the client (the challenge packet includes the
728 server's name). The client must respond with a response which
729 includes its name plus a hash value derived from the shared secret and
730 the challenge, in order to prove that it knows the secret.
732 The PPP protocol, being symmetrical, allows both peers to require the
733 other to authenticate itself. In that case, two separate and
734 independent authentication exchanges will occur. The two exchanges
735 could use different authentication protocols, and in principle,
736 different names could be used in the two exchanges.
738 The default behaviour of pppd is to agree to authenticate if
739 requested, and to not require authentication from the peer. However,
740 pppd will not agree to authenticate itself with a particular protocol
741 if it has no secrets which could be used to do so.
743 Pppd stores secrets for use in authentication in secrets
744 files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
745 Both secrets files have the same format. The secrets files can
746 contain secrets for pppd to use in authenticating itself to other
747 systems, as well as secrets for pppd to use when authenticating other
750 Each line in a secrets file contains one secret. A given secret is
751 specific to a particular combination of client and server - it can
752 only be used by that client to authenticate itself to that server.
753 Thus each line in a secrets file has at least 3 fields: the name of
754 the client, the name of the server, and the secret. These fields may
755 be followed by a list of the IP addresses that the specified client
756 may use when connecting to the specified server.
758 A secrets file is parsed into words as for a options file, so the
759 client name, server name and secrets fields must each be one word,
760 with any embedded spaces or other special characters quoted or
761 escaped. Any following words on the same line are taken to be a list
762 of acceptable IP addresses for that client. If there are only 3 words
763 on the line, or if the first word is "-", then all IP addresses are
764 disallowed. To allow any address, use "*".
765 A word starting with "!" indicates that the
766 specified address is \fInot\fR acceptable. An address may be followed
767 by "/" and a number \fIn\fR, to indicate a whole subnet, i.e. all
768 addresses which have the same value in the most significant \fIn\fR
769 bits. Note that case is significant in the client and server names
772 If the secret starts with an `@', what follows is assumed to be the
773 name of a file from which to read the secret. A "*" as the client or
774 server name matches any name. When selecting a secret, pppd takes the
775 best match, i.e. the match with the fewest wildcards.
777 Thus a secrets file contains both secrets for use in authenticating
778 other hosts, plus secrets which we use for authenticating ourselves to
779 others. When pppd is authenticating the peer (checking the peer's
780 identity), it chooses a secret with the peer's name in the first
781 field and the name of the local system in the second field. The
782 name of the local system defaults to the hostname, with the domain
783 name appended if the \fIdomain\fR option is used. This default can be
784 overridden with the \fIname\fR option, except when the
785 \fIusehostname\fR option is used.
787 When pppd is choosing a secret to use in authenticating itself to the
788 peer, it first determines what name it is going to use to identify
789 itself to the peer. This name can be specified by the user with the
790 \fIuser\fR option. If this option is not used, the name defaults to
791 the name of the local system, determined as described in the previous
792 paragraph. Then pppd looks for a secret with this name in the first
793 field and the peer's name in the second field. Pppd will know the
794 name of the peer if CHAP authentication is being used, because the
795 peer will have sent it in the challenge packet. However, if PAP is being
796 used, pppd will have to determine the peer's name from the options
797 specified by the user. The user can specify the peer's name directly
798 with the \fIremotename\fR option. Otherwise, if the remote IP address
799 was specified by a name (rather than in numeric form), that name will
800 be used as the peer's name. Failing that, pppd will use the null
801 string as the peer's name.
803 When authenticating the peer with PAP, the supplied password is first
804 compared with the secret from the secrets file. If the password
805 doesn't match the secret, the password is encrypted using crypt() and
806 checked against the secret again. Thus secrets for authenticating the
807 peer can be stored in encrypted form if desired. If the
808 \fIpapcrypt\fR option is given, the first (unencrypted) comparison is
809 omitted, for better security.
811 Furthermore, if the \fIlogin\fR option was specified, the username and
812 password are also checked against the system password database. Thus,
813 the system administrator can set up the pap-secrets file to allow PPP
814 access only to certain users, and to restrict the set of IP addresses
815 that each user can use. Typically, when using the \fIlogin\fR option,
816 the secret in /etc/ppp/pap-secrets would be "", which will match any
817 password supplied by the peer. This avoids the need to have the same
818 secret in two places.
820 Authentication must be satisfactorily completed before IPCP (or any
821 other Network Control Protocol) can be started. If the peer is
822 required to authenticate itself, and fails to do so, pppd will
823 terminated the link (by closing LCP). If IPCP negotiates an
824 unacceptable IP address for the remote host, IPCP will be closed. IP
825 packets can only be sent or received when IPCP is open.
827 In some cases it is desirable to allow some hosts which can't
828 authenticate themselves to connect and use one of a restricted set of
829 IP addresses, even when the local host generally requires
830 authentication. If the peer refuses to authenticate itself when
831 requested, pppd takes that as equivalent to authenticating with PAP
832 using the empty string for the username and password. Thus, by adding
833 a line to the pap-secrets file which specifies the empty string for
834 the client and password, it is possible to allow restricted access to
835 hosts which refuse to authenticate themselves.
838 When IPCP negotiation is completed successfully, pppd will inform the
839 kernel of the local and remote IP addresses for the ppp interface.
840 This is sufficient to create a host route to the remote end of the
841 link, which will enable the peers to exchange IP packets.
842 Communication with other machines generally requires further
843 modification to routing tables and/or ARP (Address Resolution
844 Protocol) tables. In most cases the \fIdefaultroute\fR and/or
845 \fIproxyarp\fR options are sufficient for this, but in some cases
846 further intervention is required. The /etc/ppp/ip-up script can be
849 Sometimes it is desirable to add a default route through the remote
850 host, as in the case of a machine whose only connection to the
851 Internet is through the ppp interface. The \fIdefaultroute\fR option
852 causes pppd to create such a default route when IPCP comes up, and
853 delete it when the link is terminated.
855 In some cases it is desirable to use proxy ARP, for example on a
856 server machine connected to a LAN, in order to allow other hosts to
857 communicate with the remote host. The \fIproxyarp\fR option causes
858 pppd to look for a network interface on the same subnet as the remote
859 host (an interface supporting broadcast and ARP, which is up and not a
860 point-to-point or loopback interface). If found, pppd creates a
861 permanent, published ARP entry with the IP address of the remote host
862 and the hardware address of the network interface found.
864 When the \fIdemand\fR option is used, the interface IP addresses have
865 already been set at the point when IPCP comes up. If pppd has not
866 been able to negotiate the same addresses that it used to configure
867 the interface (for example when the peer is an ISP that uses dynamic
868 IP address assignment), pppd has to change the interface IP addresses
869 to the negotiated addresses. This may disrupt existing connections,
870 and the use of demand dialling with peers that do dynamic IP address
871 assignment is not recommended.
874 The following examples assume that the /etc/ppp/options file contains
875 the \fIauth\fR option (as in the default /etc/ppp/options file in the
878 Probably the most common use of pppd is to dial out to an ISP. This
879 can be done with a command such as
883 where the /etc/ppp/peers/isp file is set up by the system
884 administrator to contain something like this:
888 connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
892 In this example, we are using chat to dial the ISP's modem and go
893 through any logon sequence required. The /etc/ppp/chat-isp file
894 contains the script used by chat; it could for example contain
907 ABORT "Username/Password Incorrect"
917 "word:" "\\qmypassword"
923 See the chat(8) man page for details of chat scripts.
925 Pppd can also be used to provide a dial-in ppp service for users. If
926 the users already have login accounts, the simplest way to set up the
927 ppp service is to let the users log in to their accounts and run pppd
928 (installed setuid-root) with a command such as
932 To allow a user to use the PPP facilities, you need to allocate an IP
933 address for that user's machine and create an entry in
934 /etc/ppp/pap-secrets or /etc/ppp/chap-secrets (depending on which
935 authentication method the PPP implementation on the user's machine
936 supports), so that the user's
937 machine can authenticate itself. For example, if Joe has a machine
938 called "joespc" which is to be allowed to dial in to the machine
939 called "server" and use the IP address joespc.my.net, you would add an
940 entry like this to /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:
942 joespc server "joe's secret" joespc.my.net
944 Alternatively, you can create a username called (for example) "ppp",
945 whose login shell is pppd and whose home directory is /etc/ppp.
946 Options to be used when pppd is run this way can be put in
949 If your serial connection is any more complicated than a piece of
950 wire, you may need to arrange for some control characters to be
951 escaped. In particular, it is often useful to escape XON (^Q) and
952 XOFF (^S), using \fIasyncmap a0000\fR. If the path includes a telnet,
953 you probably should escape ^] as well (\fIasyncmap 200a0000\fR). If
954 the path includes an rlogin, you will need to use the \fIescape ff\fR
955 option on the end which is running the rlogin client, since many
956 rlogin implementations are not transparent; they will remove the
957 sequence [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the
961 Messages are sent to the syslog daemon using facility LOG_DAEMON.
962 (This can be overriden by recompiling pppd with the macro
963 LOG_PPP defined as the desired facility.) In order to see the error
964 and debug messages, you will need to edit your /etc/syslog.conf file
965 to direct the messages to the desired output device or file.
967 The \fIdebug\fR option causes the contents of all control packets sent
968 or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
969 This can be useful if the PPP negotiation does not succeed or if
970 authentication fails.
971 If debugging is enabled at compile time, the \fIdebug\fR option also
972 causes other debugging messages to be logged.
974 Debugging can also be enabled or disabled by sending a SIGUSR1 signal
975 to the pppd process. This signal acts as a toggle.
977 Pppd invokes scripts at various stages in its processing which can be
978 used to perform site-specific ancillary processing. These scripts are
979 usually shell scripts, but could be executable code files instead.
980 Pppd does not wait for the scripts to finish. The scripts are
981 executed as root (with the real and effective user-id set to 0), so
982 that they can do things such as update routing tables or run
983 privileged daemons. Be careful that the contents of these scripts do
984 not compromise your system's security. Pppd runs the scripts with
985 standard input, output and error redirected to /dev/null, and with an
986 environment that is empty except for some environment variables that
987 give information about the link. The environment variables that pppd
991 The name of the serial tty device being used.
994 The name of the network interface being used.
997 The IP address for the local end of the link. This is only set when
1001 The IP address for the remote end of the link. This is only set when
1005 The authenticated name of the peer. This is only set if the peer
1006 authenticates itself.
1009 The baud rate of the tty device.
1012 The real user-id of the user who invoked pppd.
1014 Pppd invokes the following scripts, if they exist. It is not an error
1015 if they don't exist.
1018 A program or script which is executed after the remote system
1019 successfully authenticates itself. It is executed with the parameters
1021 \fIinterface-name peer-name user-name tty-device speed\fR
1023 Note that this script is not executed if the peer doesn't authenticate
1024 itself, for example when the \fInoauth\fR option is used.
1026 .B /etc/ppp/auth-down
1027 A program or script which is executed when the link goes down, if
1028 /etc/ppp/auth-up was previously executed. It is executed in the same
1029 manner with the same parameters as /etc/ppp/auth-up.
1032 A program or script which is executed when the link is available for
1033 sending and receiving IP packets (that is, IPCP has come up). It is
1034 executed with the parameters
1036 \fIinterface-name tty-device speed local-IP-address
1037 remote-IP-address ipparam\fR
1040 A program or script which is executed when the link is no longer
1041 available for sending and receiving IP packets. This script can be
1042 used for undoing the effects of the /etc/ppp/ip-up script. It is
1043 invoked in the same manner and with the same parameters as the ip-up
1047 A program or script which is executed when the link is available for
1048 sending and receiving IPX packets (that is, IPXCP has come up). It is
1049 executed with the parameters
1051 \fIinterface-name tty-device speed network-number local-IPX-node-address
1052 remote-IPX-node-address local-IPX-routing-protocol remote-IPX-routing-protocol
1053 local-IPX-router-name remote-IPX-router-name ipparam pppd-pid\fR
1055 The local-IPX-routing-protocol and remote-IPX-routing-protocol field
1056 may be one of the following:
1058 NONE to indicate that there is no routing protocol
1060 RIP to indicate that RIP/SAP should be used
1062 NLSP to indicate that Novell NLSP should be used
1064 RIP NLSP to indicate that both RIP/SAP and NLSP should be used
1066 .B /etc/ppp/ipx-down
1067 A program or script which is executed when the link is no longer
1068 available for sending and receiving IPX packets. This script can be
1069 used for undoing the effects of the /etc/ppp/ipx-up script. It is
1070 invoked in the same manner and with the same parameters as the ipx-up
1074 .B /var/run/ppp\fIn\fB.pid \fR(BSD or Linux), \fB/etc/ppp/ppp\fIn\fB.pid \fR(others)
1075 Process-ID for pppd process on ppp interface unit \fIn\fR.
1077 .B /etc/ppp/pap-secrets
1078 Usernames, passwords and IP addresses for PAP authentication. This
1079 file should be owned by root and not readable or writable by any other
1080 user. Pppd will log a warning if this is not the case.
1082 .B /etc/ppp/chap-secrets
1083 Names, secrets and IP addresses for CHAP authentication. As for
1084 /etc/ppp/pap-secrets, this file should be owned by root and not
1085 readable or writable by any other user. Pppd will log a warning if
1086 this is not the case.
1089 System default options for pppd, read before user default options or
1090 command-line options.
1093 User default options, read before /etc/ppp/options.\fIttyname\fR.
1095 .B /etc/ppp/options.\fIttyname
1096 System default options for the serial port being used, read after
1097 ~/.ppprc. In forming the \fIttyname\fR part of this
1098 filename, an initial /dev/ is stripped from the port name (if
1099 present), and any slashes in the remaining part are converted to
1103 A directory containing options files which may contain privileged
1104 options, even if pppd was invoked by a user other than root. The
1105 system administrator can create options files in this directory to
1106 permit non-privileged users to dial out without requiring the peer to
1107 authenticate, but only to certain trusted peers.
1112 \fICompressing TCP/IP headers for low-speed serial links.\fR
1117 .I The MD5 Message-Digest Algorithm.
1122 .I PPP Internet Protocol Control Protocol (IPCP).
1126 Lloyd, B.; Simpson, W.A.
1127 .I PPP authentication protocols.
1132 .I The Point\-to\-Point Protocol (PPP).
1137 .I PPP in HDLC-like Framing.
1140 The following signals have the specified effect when sent to pppd.
1143 These signals cause pppd to terminate the link (by closing LCP),
1144 restore the serial device settings, and exit.
1147 This signal causes pppd to terminate the link, restore the serial
1148 device settings, and close the serial device. If the \fIpersist\fR or
1149 \fIdemand\fR option has been specified, pppd will try to reopen the
1150 serial device and start another connection (after the holdoff period).
1151 Otherwise pppd will exit. If this signal is received during the
1152 holdoff period, it causes pppd to end the holdoff period immediately.
1155 This signal toggles the state of the \fIdebug\fR option.
1158 This signal causes pppd to renegotiate compression. This can be
1159 useful to re-enable compression after it has been disabled as a result
1160 of a fatal decompression error. (Fatal decompression errors generally
1161 indicate a bug in one or other implementation.)
1164 Paul Mackerras (Paul.Mackerras@cs.anu.edu.au), based on earlier work by
projects / ppp.git / blob