1PPPD(8) System Manager's Manual PPPD(8)
2
6 pppd - Point-to-Point Protocol Daemon
7
9 pppd [ options ]
10
12 PPP is the protocol used for establishing internet links over dial-up
13 modems, DSL connections, and many other types of point-to-point links.
14 The pppd daemon works together with the kernel PPP driver to establish
15 and maintain a PPP link with another system (called the peer) and to
16 negotiate Internet Protocol (IP) addresses for each end of the link.
17 Pppd can also authenticate the peer and/or supply authentication infor‐
18 mation to the peer. PPP can be used with other network protocols
19 besides IP, but such use is becoming increasingly rare.
20
22 ttyname
23 Use the serial port called ttyname to communicate with the peer.
24 If ttyname does not begin with a slash (/), the string "/dev/"
25 is prepended to ttyname to form the name of the device to open.
26 If no device name is given, or if the name of the terminal con‐
27 nected to the standard input is given, pppd will use that termi‐
28 nal, and will not fork to put itself in the background. A value
29 for this option from a privileged source cannot be overridden by
30 a non-privileged user.
31 speed An option that is a decimal number is taken as the desired baud
33 rate for the serial device. On systems such as 4.4BSD and Net‐
34 BSD, any speed can be specified. Other systems (e.g. Linux,
35 SunOS) only support the commonly-used baud rates.
36 asyncmap map
38 This option sets the Async-Control-Character-Map (ACCM) for this
39 end of the link. The ACCM is a set of 32 bits, one for each of
40 the ASCII control characters with values from 0 to 31, where a 1
41 bit indicates that the corresponding control character should
42 not be used in PPP packets sent to this system. The map is
43 encoded as a hexadecimal number (without a leading 0x) where the
44 least significant bit (00000001) represents character 0 and the
45 most significant bit (80000000) represents character 31. Pppd
46 will ask the peer to send these characters as a 2-byte escape
47 sequence. If multiple asyncmap options are given, the values
48 are ORed together. If no asyncmap option is given, the default
49 is zero, so pppd will ask the peer not to escape any control
50 characters. To escape transmitted characters, use the escape
51 option.
52 auth Require the peer to authenticate itself before allowing network
54 packets to be sent or received. This option is the default if
55 the system has a default route. If neither this option nor the
56 noauth option is specified, pppd will only allow the peer to use
57 IP addresses to which the system does not already have a route.
58 call name
60 Read additional options from the file /etc/ppp/peers/name. This
61 file may contain privileged options, such as noauth, even if
62 pppd is not being run by root. The name string may not begin
63 with / or include .. as a pathname component. The format of the
64 options file is described below.
65 connect script
67 Usually there is something which needs to be done to prepare the
68 link before the PPP protocol can be started; for instance, with
69 a dial-up modem, commands need to be sent to the modem to dial
70 the appropriate phone number. This option specifies an command
71 for pppd to execute (by passing it to a shell) before attempting
72 to start PPP negotiation. The chat (8) program is often useful
73 here, as it provides a way to send arbitrary strings to a modem
74 and respond to received characters. A value for this option
75 from a privileged source cannot be overridden by a non-privi‐
76 leged user.
77 crtscts
79 Specifies that pppd should set the serial port to use hardware
80 flow control using the RTS and CTS signals in the RS-232 inter‐
81 face. If neither the crtscts, the nocrtscts, the cdtrcts nor
82 the nocdtrcts option is given, the hardware flow control setting
83 for the serial port is left unchanged. Some serial ports (such
84 as Macintosh serial ports) lack a true RTS output. Such serial
85 ports use this mode to implement unidirectional flow control.
86 The serial port will suspend transmission when requested by the
87 modem (via CTS) but will be unable to request the modem to stop
88 sending to the computer. This mode retains the ability to use
89 DTR as a modem control line.
90 defaultroute
92 Add a default route to the system routing tables, using the peer
93 as the gateway, when IPCP negotiation is successfully completed.
94 This entry is removed when the PPP connection is broken. This
95 option is privileged if the nodefaultroute option has been spec‐
96 ified.
97 disconnect script
99 Execute the command specified by script, by passing it to a
100 shell, after pppd has terminated the link. This command could,
101 for example, issue commands to the modem to cause it to hang up
102 if hardware modem control signals were not available. The dis‐
103 connect script is not run if the modem has already hung up. A
104 value for this option from a privileged source cannot be over‐
105 ridden by a non-privileged user.
106 escape xx,yy,...
108 Specifies that certain characters should be escaped on transmis‐
109 sion (regardless of whether the peer requests them to be escaped
110 with its async control character map). The characters to be
111 escaped are specified as a list of hex numbers separated by com‐
112 mas. Note that almost any character can be specified for the
113 escape option, unlike the asyncmap option which only allows con‐
114 trol characters to be specified. The characters which may not
115 be escaped are those with hex values 0x20 - 0x3f or 0x5e.
116 file name
118 Read options from file name (the format is described below).
119 The file must be readable by the user who has invoked pppd.
120 init script
122 Execute the command specified by script, by passing it to a
123 shell, to initialize the serial line. This script would typi‐
124 cally use the chat(8) program to configure the modem to enable
125 auto answer. A value for this option from a privileged source
126 cannot be overridden by a non-privileged user.
127 lock Specifies that pppd should create a UUCP-style lock file for the
129 serial device to ensure exclusive access to the device. By
130 default, pppd will not create a lock file.
131 mru n Set the MRU [Maximum Receive Unit] value to n. Pppd will ask the
133 peer to send packets of no more than n bytes. The value of n
134 must be between 128 and 16384; the default is 1500. A value of
135 296 works well on very slow links (40 bytes for TCP/IP header +
136 256 bytes of data). Note that for the IPv6 protocol, the MRU
137 must be at least 1280.
138 mtu n Set the MTU [Maximum Transmit Unit] value to n. Unless the peer
140 requests a smaller value via MRU negotiation, pppd will request
141 that the kernel networking code send data packets of no more
142 than n bytes through the PPP network interface. Note that for
143 the IPv6 protocol, the MTU must be at least 1280.
144 passive
146 Enables the "passive" option in the LCP. With this option, pppd
147 will attempt to initiate a connection; if no reply is received
148 from the peer, pppd will then just wait passively for a valid
149 LCP packet from the peer, instead of exiting, as it would with‐
150 out this option.
151
153 <local_IP_address>:<remote_IP_address>
154 Set the local and/or remote interface IP addresses. Either one
155 may be omitted. The IP addresses can be specified with a host
156 name or in decimal dot notation (e.g. 150.234.56.78). The
157 default local address is the (first) IP address of the system
158 (unless the noipdefault option is given). The remote address
159 will be obtained from the peer if not specified in any option.
160 Thus, in simple cases, this option is not required. If a local
161 and/or remote IP address is specified with this option, pppd
162 will not accept a different value from the peer in the IPCP
163 negotiation, unless the ipcp-accept-local and/or
164 ipcp-accept-remote options are given, respectively.
165 ipv6 <local_interface_identifier>,<remote_interface_identifier>
167 Set the local and/or remote 64-bit interface identifier. Either
168 one may be omitted. The identifier must be specified in standard
169 ascii notation of IPv6 addresses (e.g. ::dead:beef). If the
170 ipv6cp-use-ipaddr option is given, the local identifier is the
171 local IPv4 address (see above). On systems which supports a
172 unique persistent id, such as EUI-48 derived from the Ethernet
173 MAC address, ipv6cp-use-persistent option can be used to replace
174 the ipv6 <local>,<remote> option. Otherwise the identifier is
175 randomized.
176 active-filter filter-expression
178 Specifies a packet filter to be applied to data packets to
179 determine which packets are to be regarded as link activity, and
180 therefore reset the idle timer, or cause the link to be brought
181 up in demand-dialling mode. This option is useful in conjunc‐
182 tion with the idle option if there are packets being sent or
183 received regularly over the link (for example, routing informa‐
184 tion packets) which would otherwise prevent the link from ever
185 appearing to be idle. The filter-expression syntax is as
186 described for tcpdump(1), except that qualifiers which are inap‐
187 propriate for a PPP link, such as ether and arp, are not permit‐
188 ted. Generally the filter expression should be enclosed in sin‐
189 gle-quotes to prevent whitespace in the expression from being
190 interpreted by the shell. This option is currently only avail‐
191 able under Linux, and requires that the kernel was configured to
192 include PPP filtering support (CONFIG_PPP_FILTER). Note that it
193 is possible to apply different constraints to incoming and out‐
194 going packets using the inbound and outbound qualifiers.
195 allow-ip address(es)
197 Allow peers to use the given IP address or subnet without
198 authenticating themselves. The parameter is parsed as for each
199 element of the list of allowed IP addresses in the secrets files
200 (see the AUTHENTICATION section below).
201 allow-number number
203 Allow peers to connect from the given telephone number. A
204 trailing `*' character will match all numbers beginning with the
205 leading part.
206 bsdcomp nr,nt
208 Request that the peer compress packets that it sends, using the
209 BSD-Compress scheme, with a maximum code size of nr bits, and
210 agree to compress packets sent to the peer with a maximum code
211 size of nt bits. If nt is not specified, it defaults to the
212 value given for nr. Values in the range 9 to 15 may be used for
213 nr and nt; larger values give better compression but consume
214 more kernel memory for compression dictionaries. Alternatively,
215 a value of 0 for nr or nt disables compression in the corre‐
216 sponding direction. Use nobsdcomp or bsdcomp 0 to disable BSD-
217 Compress compression entirely.
218 cdtrcts
220 Use a non-standard hardware flow control (i.e. DTR/CTS) to con‐
221 trol the flow of data on the serial port. If neither the
222 crtscts, the nocrtscts, the cdtrcts nor the nocdtrcts option is
223 given, the hardware flow control setting for the serial port is
224 left unchanged. Some serial ports (such as Macintosh serial
225 ports) lack a true RTS output. Such serial ports use this mode
226 to implement true bi-directional flow control. The sacrifice is
227 that this flow control mode does not permit using DTR as a modem
228 control line.
229 chap-interval n
231 If this option is given, pppd will rechallenge the peer every n
232 seconds.
233 chap-max-challenge n
235 Set the maximum number of CHAP challenge transmissions to n
236 (default 10).
237 chap-restart n
239 Set the CHAP restart interval (retransmission timeout for chal‐
240 lenges) to n seconds (default 3).
241 child-timeout n
243 When exiting, wait for up to n seconds for any child processes
244 (such as the command specified with the pty command) to exit
245 before exiting. At the end of the timeout, pppd will send a
246 SIGTERM signal to any remaining child processes and exit. A
247 value of 0 means no timeout, that is, pppd will wait until all
248 child processes have exited.
249 connect-delay n
251 Wait for up to n milliseconds after the connect script finishes
252 for a valid PPP packet from the peer. At the end of this time,
253 or when a valid PPP packet is received from the peer, pppd will
254 commence negotiation by sending its first LCP packet. The
255 default value is 1000 (1 second). This wait period only applies
256 if the connect or pty option is used.
257 debug Enables connection debugging facilities. If this option is
259 given, pppd will log the contents of all control packets sent or
260 received in a readable form. The packets are logged through
261 syslog with facility daemon and level debug. This information
262 can be directed to a file by setting up /etc/syslog.conf appro‐
263 priately (see syslog.conf(5)).
264 default-asyncmap
266 Disable asyncmap negotiation, forcing all control characters to
267 be escaped for both the transmit and the receive direction.
268 default-mru
270 Disable MRU [Maximum Receive Unit] negotiation. With this
271 option, pppd will use the default MRU value of 1500 bytes for
272 both the transmit and receive direction.
273 deflate nr,nt
275 Request that the peer compress packets that it sends, using the
276 Deflate scheme, with a maximum window size of 2**nr bytes, and
277 agree to compress packets sent to the peer with a maximum window
278 size of 2**nt bytes. If nt is not specified, it defaults to the
279 value given for nr. Values in the range 9 to 15 may be used for
280 nr and nt; larger values give better compression but consume
281 more kernel memory for compression dictionaries. Alternatively,
282 a value of 0 for nr or nt disables compression in the corre‐
283 sponding direction. Use nodeflate or deflate 0 to disable
284 Deflate compression entirely. (Note: pppd requests Deflate com‐
285 pression in preference to BSD-Compress if the peer can do
286 either.)
287 demand Initiate the link only on demand, i.e. when data traffic is
289 present. With this option, the remote IP address must be speci‐
290 fied by the user on the command line or in an options file.
291 Pppd will initially configure the interface and enable it for IP
292 traffic without connecting to the peer. When traffic is avail‐
293 able, pppd will connect to the peer and perform negotiation,
294 authentication, etc. When this is completed, pppd will commence
295 passing data packets (i.e., IP packets) across the link.
296 The demand option implies the persist option. If this behaviour
298 is not desired, use the nopersist option after the demand
299 option. The idle and holdoff options are also useful in conjuc‐
300 tion with the demand option.
301 domain d
303 Append the domain name d to the local host name for authentica‐
304 tion purposes. For example, if gethostname() returns the name
305 porsche, but the fully qualified domain name is
306 porsche.Quotron.COM, you could specify domain Quotron.COM. Pppd
307 would then use the name porsche.Quotron.COM for looking up
308 secrets in the secrets file, and as the default name to send to
309 the peer when authenticating itself to the peer. This option is
310 privileged.
311 dryrun With the dryrun option, pppd will print out all the option val‐
313 ues which have been set and then exit, after parsing the command
314 line and options files and checking the option values, but
315 before initiating the link. The option values are logged at
316 level info, and also printed to standard output unless the
317 device on standard output is the device that pppd would be using
318 to communicate with the peer.
319 dump With the dump option, pppd will print out all the option values
321 which have been set. This option is like the dryrun option
322 except that pppd proceeds as normal rather than exiting.
323 endpoint <epdisc>
325 Sets the endpoint discriminator sent by the local machine to the
326 peer during multilink negotiation to <epdisc>. The default is
327 to use the MAC address of the first ethernet interface on the
328 system, if any, otherwise the IPv4 address corresponding to the
329 hostname, if any, provided it is not in the multicast or
330 locally-assigned IP address ranges, or the localhost address.
331 The endpoint discriminator can be the string null or of the form
332 type:value, where type is a decimal number or one of the strings
333 local, IP, MAC, magic, or phone. The value is an IP address in
334 dotted-decimal notation for the IP type, or a string of bytes in
335 hexadecimal, separated by periods or colons for the other types.
336 For the MAC type, the value may also be the name of an ethernet
337 or similar network interface. This option is currently only
338 available under Linux.
339 eap-interval n
341 If this option is given and pppd authenticates the peer with EAP
342 (i.e., is the server), pppd will restart EAP authentication
343 every n seconds. For EAP SRP-SHA1, see also the srp-interval
344 option, which enables lightweight rechallenge.
345 eap-max-rreq n
347 Set the maximum number of EAP Requests to which pppd will
348 respond (as a client) without hearing EAP Success or Failure.
349 (Default is 20.)
350 eap-max-sreq n
352 Set the maximum number of EAP Requests that pppd will issue (as
353 a server) while attempting authentication. (Default is 10.)
354 eap-restart n
356 Set the retransmit timeout for EAP Requests when acting as a
357 server (authenticator). (Default is 3 seconds.)
358 eap-timeout n
360 Set the maximum time to wait for the peer to send an EAP Request
361 when acting as a client (authenticatee). (Default is 20 sec‐
362 onds.)
363 hide-password
365 When logging the contents of PAP packets, this option causes
366 pppd to exclude the password string from the log. This is the
367 default.
368 holdoff n
370 Specifies how many seconds to wait before re-initiating the link
371 after it terminates. This option only has any effect if the
372 persist or demand option is used. The holdoff period is not
373 applied if the link was terminated because it was idle.
374 idle n Specifies that pppd should disconnect if the link is idle for n
376 seconds. The link is idle when no data packets (i.e. IP pack‐
377 ets) are being sent or received. Note: it is not advisable to
378 use this option with the persist option without the demand
379 option. If the active-filter option is given, data packets
380 which are rejected by the specified activity filter also count
381 as the link being idle.
382 ipcp-accept-local
384 With this option, pppd will accept the peer's idea of our local
385 IP address, even if the local IP address was specified in an
386 option.
387 ipcp-accept-remote
389 With this option, pppd will accept the peer's idea of its
390 (remote) IP address, even if the remote IP address was specified
391 in an option.
392 ipcp-max-configure n
394 Set the maximum number of IPCP configure-request transmissions
395 to n (default 10).
396 ipcp-max-failure n
398 Set the maximum number of IPCP configure-NAKs returned before
399 starting to send configure-Rejects instead to n (default 10).
400 ipcp-max-terminate n
402 Set the maximum number of IPCP terminate-request transmissions
403 to n (default 3).
404 ipcp-restart n
406 Set the IPCP restart interval (retransmission timeout) to n sec‐
407 onds (default 3).
408 ipparam string
410 Provides an extra parameter to the ip-up, ip-pre-up and ip-down
411 scripts. If this option is given, the string supplied is given
412 as the 6th parameter to those scripts.
413 ipv6cp-max-configure n
415 Set the maximum number of IPv6CP configure-request transmissions
416 to n (default 10).
417 ipv6cp-max-failure n
419 Set the maximum number of IPv6CP configure-NAKs returned before
420 starting to send configure-Rejects instead to n (default 10).
421 ipv6cp-max-terminate n
423 Set the maximum number of IPv6CP terminate-request transmissions
424 to n (default 3).
425 ipv6cp-restart n
427 Set the IPv6CP restart interval (retransmission timeout) to n
428 seconds (default 3).
429 ipx Enable the IPXCP and IPX protocols. This option is presently
431 only supported under Linux, and only if your kernel has been
432 configured to include IPX support.
433 ipx-network n
435 Set the IPX network number in the IPXCP configure request frame
436 to n, a hexadecimal number (without a leading 0x). There is no
437 valid default. If this option is not specified, the network
438 number is obtained from the peer. If the peer does not have the
439 network number, the IPX protocol will not be started.
440 ipx-node n:m
442 Set the IPX node numbers. The two node numbers are separated
443 from each other with a colon character. The first number n is
444 the local node number. The second number m is the peer's node
445 number. Each node number is a hexadecimal number, at most 10
446 digits long. The node numbers on the ipx-network must be unique.
447 There is no valid default. If this option is not specified then
448 the node numbers are obtained from the peer.
449 ipx-router-name <string>
451 Set the name of the router. This is a string and is sent to the
452 peer as information data.
453 ipx-routing n
455 Set the routing protocol to be received by this option. More
456 than one instance of ipx-routing may be specified. The 'none'
457 option (0) may be specified as the only instance of ipx-routing.
458 The values may be 0 for NONE, 2 for RIP/SAP, and 4 for NLSP.
459 ipxcp-accept-local
461 Accept the peer's NAK for the node number specified in the
462 ipx-node option. If a node number was specified, and non-zero,
463 the default is to insist that the value be used. If you include
464 this option then you will permit the peer to override the entry
465 of the node number.
466 ipxcp-accept-network
468 Accept the peer's NAK for the network number specified in the
469 ipx-network option. If a network number was specified, and non-
470 zero, the default is to insist that the value be used. If you
471 include this option then you will permit the peer to override
472 the entry of the node number.
473 ipxcp-accept-remote
475 Use the peer's network number specified in the configure request
476 frame. If a node number was specified for the peer and this
477 option was not specified, the peer will be forced to use the
478 value which you have specified.
479 ipxcp-max-configure n
481 Set the maximum number of IPXCP configure request frames which
482 the system will send to n. The default is 10.
483 ipxcp-max-failure n
485 Set the maximum number of IPXCP NAK frames which the local sys‐
486 tem will send before it rejects the options. The default value
487 is 3.
488 ipxcp-max-terminate n
490 Set the maximum nuber of IPXCP terminate request frames before
491 the local system considers that the peer is not listening to
492 them. The default value is 3.
493 kdebug n
495 Enable debugging code in the kernel-level PPP driver. The argu‐
496 ment values depend on the specific kernel driver, but in general
497 a value of 1 will enable general kernel debug messages. (Note
498 that these messages are usually only useful for debugging the
499 kernel driver itself.) For the Linux 2.2.x kernel driver, the
500 value is a sum of bits: 1 to enable general debug messages, 2 to
501 request that the contents of received packets be printed, and 4
502 to request that the contents of transmitted packets be printed.
503 On most systems, messages printed by the kernel are logged by
504 syslog(1) to a file as directed in the /etc/syslog.conf configu‐
505 ration file.
506 ktune Enables pppd to alter kernel settings as appropriate. Under
508 Linux, pppd will enable IP forwarding (i.e. set
509 /proc/sys/net/ipv4/ip_forward to 1) if the proxyarp option is
510 used, and will enable the dynamic IP address option (i.e. set
511 /proc/sys/net/ipv4/ip_dynaddr to 1) in demand mode if the local
512 address changes.
513 lcp-echo-failure n
515 If this option is given, pppd will presume the peer to be dead
516 if n LCP echo-requests are sent without receiving a valid LCP
517 echo-reply. If this happens, pppd will terminate the connec‐
518 tion. Use of this option requires a non-zero value for the
519 lcp-echo-interval parameter. This option can be used to enable
520 pppd to terminate after the physical connection has been broken
521 (e.g., the modem has hung up) in situations where no hardware
522 modem control lines are available.
523 lcp-echo-interval n
525 If this option is given, pppd will send an LCP echo-request
526 frame to the peer every n seconds. Normally the peer should
527 respond to the echo-request by sending an echo-reply. This
528 option can be used with the lcp-echo-failure option to detect
529 that the peer is no longer connected.
530 lcp-max-configure n
532 Set the maximum number of LCP configure-request transmissions to
533 n (default 10).
534 lcp-max-failure n
536 Set the maximum number of LCP configure-NAKs returned before
537 starting to send configure-Rejects instead to n (default 10).
538 lcp-max-terminate n
540 Set the maximum number of LCP terminate-request transmissions to
541 n (default 3).
542 lcp-restart n
544 Set the LCP restart interval (retransmission timeout) to n sec‐
545 onds (default 3).
546 linkname name
548 Sets the logical name of the link to name. Pppd will create a
549 file named ppp-name.pid in /var/run (or /etc/ppp on some sys‐
550 tems) containing its process ID. This can be useful in deter‐
551 mining which instance of pppd is responsible for the link to a
552 given peer system. This is a privileged option.
553 local Don't use the modem control lines. With this option, pppd will
555 ignore the state of the CD (Carrier Detect) signal from the
556 modem and will not change the state of the DTR (Data Terminal
557 Ready) signal. This is the opposite of the modem option.
558 logfd n
560 Send log messages to file descriptor n. Pppd will send log mes‐
561 sages to at most one file or file descriptor (as well as sending
562 the log messages to syslog), so this option and the logfile
563 option are mutually exclusive. The default is for pppd to send
564 log messages to stdout (file descriptor 1), unless the serial
565 port is already open on stdout.
566 logfile filename
568 Append log messages to the file filename (as well as sending the
569 log messages to syslog). The file is opened with the privileges
570 of the user who invoked pppd, in append mode.
571 login Use the system password database for authenticating the peer
573 using PAP, and record the user in the system wtmp file. Note
574 that the peer must have an entry in the /etc/ppp/pap-secrets
575 file as well as the system password database to be allowed
576 access.
577 maxconnect n
579 Terminate the connection when it has been available for network
580 traffic for n seconds (i.e. n seconds after the first network
581 control protocol comes up).
582 maxfail n
584 Terminate after n consecutive failed connection attempts. A
585 value of 0 means no limit. The default value is 10.
586 modem Use the modem control lines. This option is the default. With
588 this option, pppd will wait for the CD (Carrier Detect) signal
589 from the modem to be asserted when opening the serial device
590 (unless a connect script is specified), and it will drop the DTR
591 (Data Terminal Ready) signal briefly when the connection is ter‐
592 minated and before executing the connect script. On Ultrix,
593 this option implies hardware flow control, as for the crtscts
594 option. This is the opposite of the local option.
595 mp Enables the use of PPP multilink; this is an alias for the `mul‐
597 tilink' option. This option is currently only available under
598 Linux.
599 mppe-stateful
601 Allow MPPE to use stateful mode. Stateless mode is still
602 attempted first. The default is to disallow stateful mode.
603 mpshortseq
605 Enables the use of short (12-bit) sequence numbers in multilink
606 headers, as opposed to 24-bit sequence numbers. This option is
607 only available under Linux, and only has any effect if multilink
608 is enabled (see the multilink option).
609 mrru n Sets the Maximum Reconstructed Receive Unit to n. The MRRU is
611 the maximum size for a received packet on a multilink bundle,
612 and is analogous to the MRU for the individual links. This
613 option is currently only available under Linux, and only has any
614 effect if multilink is enabled (see the multilink option).
615 ms-dns <addr>
617 If pppd is acting as a server for Microsoft Windows clients,
618 this option allows pppd to supply one or two DNS (Domain Name
619 Server) addresses to the clients. The first instance of this
620 option specifies the primary DNS address; the second instance
621 (if given) specifies the secondary DNS address. (This option
622 was present in some older versions of pppd under the name
623 dns-addr.)
624 ms-wins <addr>
626 If pppd is acting as a server for Microsoft Windows or "Samba"
627 clients, this option allows pppd to supply one or two WINS (Win‐
628 dows Internet Name Services) server addresses to the clients.
629 The first instance of this option specifies the primary WINS
630 address; the second instance (if given) specifies the secondary
631 WINS address.
632 multilink
634 Enables the use of the PPP multilink protocol. If the peer also
635 supports multilink, then this link can become part of a bundle
636 between the local system and the peer. If there is an existing
637 bundle to the peer, pppd will join this link to that bundle,
638 otherwise pppd will create a new bundle. See the MULTILINK sec‐
639 tion below. This option is currently only available under
640 Linux.
641 name name
643 Set the name of the local system for authentication purposes to
644 name. This is a privileged option. With this option, pppd will
645 use lines in the secrets files which have name as the second
646 field when looking for a secret to use in authenticating the
647 peer. In addition, unless overridden with the user option, name
648 will be used as the name to send to the peer when authenticating
649 the local system to the peer. (Note that pppd does not append
650 the domain name to name.)
651 noaccomp
653 Disable Address/Control compression in both directions (send and
654 receive).
655 noauth Do not require the peer to authenticate itself. This option is
657 privileged.
658 nobsdcomp
660 Disables BSD-Compress compression; pppd will not request or
661 agree to compress packets using the BSD-Compress scheme.
662 noccp Disable CCP (Compression Control Protocol) negotiation. This
664 option should only be required if the peer is buggy and gets
665 confused by requests from pppd for CCP negotiation.
666 nocrtscts
668 Disable hardware flow control (i.e. RTS/CTS) on the serial port.
669 If neither the crtscts nor the nocrtscts nor the cdtrcts nor the
670 nocdtrcts option is given, the hardware flow control setting for
671 the serial port is left unchanged.
672 nocdtrcts
674 This option is a synonym for nocrtscts. Either of these options
675 will disable both forms of hardware flow control.
676 nodefaultroute
678 Disable the defaultroute option. The system administrator who
679 wishes to prevent users from creating default routes with pppd
680 can do so by placing this option in the /etc/ppp/options file.
681 nodeflate
683 Disables Deflate compression; pppd will not request or agree to
684 compress packets using the Deflate scheme.
685 nodetach
687 Don't detach from the controlling terminal. Without this
688 option, if a serial device other than the terminal on the stan‐
689 dard input is specified, pppd will fork to become a background
690 process.
691 noendpoint
693 Disables pppd from sending an endpoint discriminator to the peer
694 or accepting one from the peer (see the MULTILINK section
695 below). This option should only be required if the peer is
696 buggy.
697 noip Disable IPCP negotiation and IP communication. This option
699 should only be required if the peer is buggy and gets confused
700 by requests from pppd for IPCP negotiation.
701 noipv6 Disable IPv6CP negotiation and IPv6 communication. This option
703 should only be required if the peer is buggy and gets confused
704 by requests from pppd for IPv6CP negotiation.
705 noipdefault
707 Disables the default behaviour when no local IP address is spec‐
708 ified, which is to determine (if possible) the local IP address
709 from the hostname. With this option, the peer will have to sup‐
710 ply the local IP address during IPCP negotiation (unless it
711 specified explicitly on the command line or in an options file).
712 noipx Disable the IPXCP and IPX protocols. This option should only be
714 required if the peer is buggy and gets confused by requests from
715 pppd for IPXCP negotiation.
716 noktune
718 Opposite of the ktune option; disables pppd from changing system
719 settings.
720 nolock Opposite of the lock option; specifies that pppd should not cre‐
722 ate a UUCP-style lock file for the serial device. This option
723 is privileged.
724 nolog Do not send log messages to a file or file descriptor. This
726 option cancels the logfd and logfile options.
727 nomagic
729 Disable magic number negotiation. With this option, pppd cannot
730 detect a looped-back line. This option should only be needed if
731 the peer is buggy.
732 nomp Disables the use of PPP multilink. This option is currently
734 only available under Linux.
735 nomppe Disables MPPE (Microsoft Point to Point Encryption). This is
737 the default.
738 nomppe-40
740 Disable 40-bit encryption with MPPE.
741 nomppe-128
743 Disable 128-bit encryption with MPPE.
744 nomppe-stateful
746 Disable MPPE stateful mode. This is the default.
747 nompshortseq
749 Disables the use of short (12-bit) sequence numbers in the PPP
750 multilink protocol, forcing the use of 24-bit sequence numbers.
751 This option is currently only available under Linux, and only
752 has any effect if multilink is enabled.
753 nomultilink
755 Disables the use of PPP multilink. This option is currently
756 only available under Linux.
757 nopcomp
759 Disable protocol field compression negotiation in both the
760 receive and the transmit direction.
761 nopersist
763 Exit once a connection has been made and terminated. This is
764 the default unless the persist or demand option has been speci‐
765 fied.
766 nopredictor1
768 Do not accept or agree to Predictor-1 compression.
769 noproxyarp
771 Disable the proxyarp option. The system administrator who
772 wishes to prevent users from creating proxy ARP entries with
773 pppd can do so by placing this option in the /etc/ppp/options
774 file.
775 notty Normally, pppd requires a terminal device. With this option,
777 pppd will allocate itself a pseudo-tty master/slave pair and use
778 the slave as its terminal device. Pppd will create a child
779 process to act as a `character shunt' to transfer characters
780 between the pseudo-tty master and its standard input and output.
781 Thus pppd will transmit characters on its standard output and
782 receive characters on its standard input even if they are not
783 terminal devices. This option increases the latency and CPU
784 overhead of transferring data over the ppp interface as all of
785 the characters sent and received must flow through the character
786 shunt process. An explicit device name may not be given if this
787 option is used.
788 novj Disable Van Jacobson style TCP/IP header compression in both the
790 transmit and the receive direction.
791 novjccomp
793 Disable the connection-ID compression option in Van Jacobson
794 style TCP/IP header compression. With this option, pppd will
795 not omit the connection-ID byte from Van Jacobson compressed
796 TCP/IP headers, nor ask the peer to do so.
797 papcrypt
799 Indicates that all secrets in the /etc/ppp/pap-secrets file
800 which are used for checking the identity of the peer are
801 encrypted, and thus pppd should not accept a password which,
802 before encryption, is identical to the secret from the
803 /etc/ppp/pap-secrets file.
804 pap-max-authreq n
806 Set the maximum number of PAP authenticate-request transmissions
807 to n (default 10).
808 pap-restart n
810 Set the PAP restart interval (retransmission timeout) to n sec‐
811 onds (default 3).
812 pap-timeout n
814 Set the maximum time that pppd will wait for the peer to authen‐
815 ticate itself with PAP to n seconds (0 means no limit).
816 pass-filter filter-expression
818 Specifies a packet filter to applied to data packets being sent
819 or received to determine which packets should be allowed to
820 pass. Packets which are rejected by the filter are silently
821 discarded. This option can be used to prevent specific network
822 daemons (such as routed) using up link bandwidth, or to provide
823 a very basic firewall capability. The filter-expression syntax
824 is as described for tcpdump(1), except that qualifiers which are
825 inappropriate for a PPP link, such as ether and arp, are not
826 permitted. Generally the filter expression should be enclosed
827 in single-quotes to prevent whitespace in the expression from
828 being interpreted by the shell. Note that it is possible to
829 apply different constraints to incoming and outgoing packets
830 using the inbound and outbound qualifiers. This option is cur‐
831 rently only available under Linux, and requires that the kernel
832 was configured to include PPP filtering support (CONFIG_PPP_FIL‐
833 TER).
834 password password-string
836 Specifies the password to use for authenticating to the peer.
837 Use of this option is discouraged, as the password is likely to
838 be visible to other users on the system (for example, by using
839 ps(1)).
840 persist
842 Do not exit after a connection is terminated; instead try to
843 reopen the connection. The maxfail option still has an effect on
844 persistent connections.
845 plugin filename
847 Load the shared library object file filename as a plugin. This
848 is a privileged option. If filename does not contain a slash
849 (/), pppd will look in the /usr/lib/pppd/version directory for
850 the plugin, where version is the version number of pppd (for
851 example, 2.4.2).
852 predictor1
854 Request that the peer compress frames that it sends using Pre‐
855 dictor-1 compression, and agree to compress transmitted frames
856 with Predictor-1 if requested. This option has no effect unless
857 the kernel driver supports Predictor-1 compression.
858 privgroup group-name
860 Allows members of group group-name to use privileged options.
861 This is a privileged option. Use of this option requires care
862 as there is no guarantee that members of group-name cannot use
863 pppd to become root themselves. Consider it equivalent to
864 putting the members of group-name in the kmem or disk group.
865 proxyarp
867 Add an entry to this system's ARP [Address Resolution Protocol]
868 table with the IP address of the peer and the Ethernet address
869 of this system. This will have the effect of making the peer
870 appear to other systems to be on the local ethernet.
871 pty script
873 Specifies that the command script is to be used to communicate
874 rather than a specific terminal device. Pppd will allocate
875 itself a pseudo-tty master/slave pair and use the slave as its
876 terminal device. The script will be run in a child process with
877 the pseudo-tty master as its standard input and output. An
878 explicit device name may not be given if this option is used.
879 (Note: if the record option is used in conjuction with the pty
880 option, the child process will have pipes on its standard input
881 and output.)
882 receive-all
884 With this option, pppd will accept all control characters from
885 the peer, including those marked in the receive asyncmap. With‐
886 out this option, pppd will discard those characters as specified
887 in RFC1662. This option should only be needed if the peer is
888 buggy.
889 record filename
891 Specifies that pppd should record all characters sent and
892 received to a file named filename. This file is opened in
893 append mode, using the user's user-ID and permissions. This
894 option is implemented using a pseudo-tty and a process to trans‐
895 fer characters between the pseudo-tty and the real serial
896 device, so it will increase the latency and CPU overhead of
897 transferring data over the ppp interface. The characters are
898 stored in a tagged format with timestamps, which can be dis‐
899 played in readable form using the pppdump(8) program.
900 remotename name
902 Set the assumed name of the remote system for authentication
903 purposes to name.
904 remotenumber number
906 Set the assumed telephone number of the remote system for
907 authentication purposes to number.
908 refuse-chap
910 With this option, pppd will not agree to authenticate itself to
911 the peer using CHAP.
912 refuse-mschap
914 With this option, pppd will not agree to authenticate itself to
915 the peer using MS-CHAP.
916 refuse-mschap-v2
918 With this option, pppd will not agree to authenticate itself to
919 the peer using MS-CHAPv2.
920 refuse-eap
922 With this option, pppd will not agree to authenticate itself to
923 the peer using EAP.
924 refuse-pap
926 With this option, pppd will not agree to authenticate itself to
927 the peer using PAP.
928 require-chap
930 Require the peer to authenticate itself using CHAP [Challenge
931 Handshake Authentication Protocol] authentication.
932 require-mppe
934 Require the use of MPPE (Microsoft Point to Point Encryption).
935 This option disables all other compression types. This option
936 enables both 40-bit and 128-bit encryption. In order for MPPE
937 to successfully come up, you must have authenticated with either
938 MS-CHAP or MS-CHAPv2. This option is presently only supported
939 under Linux, and only if your kernel has been configured to
940 include MPPE support.
941 require-mppe-40
943 Require the use of MPPE, with 40-bit encryption.
944 require-mppe-128
946 Require the use of MPPE, with 128-bit encryption.
947 require-mschap
949 Require the peer to authenticate itself using MS-CHAP [Microsoft
950 Challenge Handshake Authentication Protocol] authentication.
951 require-mschap-v2
953 Require the peer to authenticate itself using MS-CHAPv2 [Micro‐
954 soft Challenge Handshake Authentication Protocol, Version 2]
955 authentication.
956 require-eap
958 Require the peer to authenticate itself using EAP [Extensible
959 Authentication Protocol] authentication.
960 require-pap
962 Require the peer to authenticate itself using PAP [Password
963 Authentication Protocol] authentication.
964 show-password
966 When logging the contents of PAP packets, this option causes
967 pppd to show the password string in the log message.
968 silent With this option, pppd will not transmit LCP packets to initiate
970 a connection until a valid LCP packet is received from the peer
971 (as for the `passive' option with ancient versions of pppd).
972 srp-interval n
974 If this parameter is given and pppd uses EAP SRP-SHA1 to authen‐
975 ticate the peer (i.e., is the server), then pppd will use the
976 optional lightweight SRP rechallenge mechanism at intervals of n
977 seconds. This option is faster than eap-interval reauthentica‐
978 tion because it uses a hash-based mechanism and does not derive
979 a new session key.
980 srp-pn-secret string
982 Set the long-term pseudonym-generating secret for the server.
983 This value is optional and if set, needs to be known at the
984 server (authenticator) side only, and should be different for
985 each server (or poll of identical servers). It is used along
986 with the current date to generate a key to encrypt and decrypt
987 the client's identity contained in the pseudonym.
988 srp-use-pseudonym
990 When operating as an EAP SRP-SHA1 client, attempt to use the
991 pseudonym stored in ~/.ppp_psuedonym first as the identity, and
992 save in this file any pseudonym offered by the peer during
993 authentication.
994 sync Use synchronous HDLC serial encoding instead of asynchronous.
996 The device used by pppd with this option must have sync support.
997 Currently supports Microgate SyncLink adapters under Linux and
998 FreeBSD 2.2.8 and later.
999 unit num
1001 Sets the ppp unit number (for a ppp0 or ppp1 etc interface name)
1002 for outbound connections.
1003 updetach
1005 With this option, pppd will detach from its controlling terminal
1006 once it has successfully established the ppp connection (to the
1007 point where the first network control protocol, usually the IP
1008 control protocol, has come up).
1009 usehostname
1011 Enforce the use of the hostname (with domain name appended, if
1012 given) as the name of the local system for authentication pur‐
1013 poses (overrides the name option). This option is not normally
1014 needed since the name option is privileged.
1015 usepeerdns
1017 Ask the peer for up to 2 DNS server addresses. The addresses
1018 supplied by the peer (if any) are passed to the /etc/ppp/ip-up
1019 script in the environment variables DNS1 and DNS2, and the envi‐
1020 ronment variable USEPEERDNS will be set to 1. In addition, pppd
1021 will create an /var/run/ppp/resolv.conf file containing one or
1022 two nameserver lines with the address(es) supplied by the peer.
1023 user name
1025 Sets the name used for authenticating the local system to the
1026 peer to name.
1027 vj-max-slots n
1029 Sets the number of connection slots to be used by the Van Jacob‐
1030 son TCP/IP header compression and decompression code to n, which
1031 must be between 2 and 16 (inclusive).
1032 welcome script
1034 Run the executable or shell command specified by script before
1035 initiating PPP negotiation, after the connect script (if any)
1036 has completed. A value for this option from a privileged source
1037 cannot be overridden by a non-privileged user.
1038 xonxoff
1040 Use software flow control (i.e. XON/XOFF) to control the flow of
1041 data on the serial port.
1042
1044 Options can be taken from files as well as the command line. Pppd
1045 reads options from the files /etc/ppp/options, ~/.ppprc and
1046 /etc/ppp/options.ttyname (in that order) before processing the options
1047 on the command line. (In fact, the command-line options are scanned to
1048 find the terminal name before the options.ttyname file is read.) In
1049 forming the name of the options.ttyname file, the initial /dev/ is
1050 removed from the terminal name, and any remaining / characters are
1051 replaced with dots.
1052 An options file is parsed into a series of words, delimited by white‐
1054 space. Whitespace can be included in a word by enclosing the word in
1055 double-quotes ("). A backslash (\) quotes the following character. A
1056 hash (#) starts a comment, which continues until the end of the line.
1057 There is no restriction on using the file or call options within an
1058 options file.
1059
1061 pppd provides system administrators with sufficient access control that
1062 PPP access to a server machine can be provided to legitimate users
1063 without fear of compromising the security of the server or the network
1064 it's on. This control is provided through restrictions on which IP
1065 addresses the peer may use, based on its authenticated identity (if
1066 any), and through restrictions on which options a non-privileged user
1067 may use. Several of pppd's options are privileged, in particular those
1068 which permit potentially insecure configurations; these options are
1069 only accepted in files which are under the control of the system admin‐
1070 istrator, or if pppd is being run by root.
1071 The default behaviour of pppd is to allow an unauthenticated peer to
1073 use a given IP address only if the system does not already have a route
1074 to that IP address. For example, a system with a permanent connection
1075 to the wider internet will normally have a default route, and thus all
1076 peers will have to authenticate themselves in order to set up a connec‐
1077 tion. On such a system, the auth option is the default. On the other
1078 hand, a system where the PPP link is the only connection to the inter‐
1079 net will not normally have a default route, so the peer will be able to
1080 use almost any IP address without authenticating itself.
1081 As indicated above, some security-sensitive options are privileged,
1083 which means that they may not be used by an ordinary non-privileged
1084 user running a setuid-root pppd, either on the command line, in the
1085 user's ~/.ppprc file, or in an options file read using the file option.
1086 Privileged options may be used in /etc/ppp/options file or in an
1087 options file read using the call option. If pppd is being run by the
1088 root user, privileged options can be used without restriction.
1089 When opening the device, pppd uses either the invoking user's user ID
1091 or the root UID (that is, 0), depending on whether the device name was
1092 specified by the user or the system administrator. If the device name
1093 comes from a privileged source, that is, /etc/ppp/options or an options
1094 file read using the call option, pppd uses full root privileges when
1095 opening the device. Thus, by creating an appropriate file under
1096 /etc/ppp/peers, the system administrator can allow users to establish a
1097 ppp connection via a device which they would not normally have permis‐
1098 sion to access. Otherwise pppd uses the invoking user's real UID when
1099 opening the device.
1100
1102 Authentication is the process whereby one peer convinces the other of
1103 its identity. This involves the first peer sending its name to the
1104 other, together with some kind of secret information which could only
1105 come from the genuine authorized user of that name. In such an
1106 exchange, we will call the first peer the "client" and the other the
1107 "server". The client has a name by which it identifies itself to the
1108 server, and the server also has a name by which it identifies itself to
1109 the client. Generally the genuine client shares some secret (or pass‐
1110 word) with the server, and authenticates itself by proving that it
1111 knows that secret. Very often, the names used for authentication cor‐
1112 respond to the internet hostnames of the peers, but this is not essen‐
1113 tial.
1114 At present, pppd supports three authentication protocols: the Password
1116 Authentication Protocol (PAP), Challenge Handshake Authentication Pro‐
1117 tocol (CHAP), and Extensible Authentication Protocol (EAP). PAP
1118 involves the client sending its name and a cleartext password to the
1119 server to authenticate itself. In contrast, the server initiates the
1120 CHAP authentication exchange by sending a challenge to the client (the
1121 challenge packet includes the server's name). The client must respond
1122 with a response which includes its name plus a hash value derived from
1123 the shared secret and the challenge, in order to prove that it knows
1124 the secret. EAP supports CHAP-style authentication, and also includes
1125 the SRP-SHA1 mechanism, which is resistant to dictionary-based attacks
1126 and does not require a cleartext password on the server side.
1127 The PPP protocol, being symmetrical, allows both peers to require the
1129 other to authenticate itself. In that case, two separate and indepen‐
1130 dent authentication exchanges will occur. The two exchanges could use
1131 different authentication protocols, and in principle, different names
1132 could be used in the two exchanges.
1133 The default behaviour of pppd is to agree to authenticate if requested,
1135 and to not require authentication from the peer. However, pppd will
1136 not agree to authenticate itself with a particular protocol if it has
1137 no secrets which could be used to do so.
1138 Pppd stores secrets for use in authentication in secrets files
1140 (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP, MS-CHAP,
1141 MS-CHAPv2, and EAP MD5-Challenge, and /etc/ppp/srp-secrets for EAP
1142 SRP-SHA1). All secrets files have the same format. The secrets files
1143 can contain secrets for pppd to use in authenticating itself to other
1144 systems, as well as secrets for pppd to use when authenticating other
1145 systems to itself.
1146 Each line in a secrets file contains one secret. A given secret is
1148 specific to a particular combination of client and server - it can only
1149 be used by that client to authenticate itself to that server. Thus
1150 each line in a secrets file has at least 3 fields: the name of the
1151 client, the name of the server, and the secret. These fields may be
1152 followed by a list of the IP addresses that the specified client may
1153 use when connecting to the specified server.
1154 A secrets file is parsed into words as for a options file, so the
1156 client name, server name and secrets fields must each be one word, with
1157 any embedded spaces or other special characters quoted or escaped.
1158 Note that case is significant in the client and server names and in the
1159 secret.
1160 If the secret starts with an `@', what follows is assumed to be the
1162 name of a file from which to read the secret. A "*" as the client or
1163 server name matches any name. When selecting a secret, pppd takes the
1164 best match, i.e. the match with the fewest wildcards.
1165 Any following words on the same line are taken to be a list of accept‐
1167 able IP addresses for that client. If there are only 3 words on the
1168 line, or if the first word is "-", then all IP addresses are disal‐
1169 lowed. To allow any address, use "*". A word starting with "!" indi‐
1170 cates that the specified address is not acceptable. An address may be
1171 followed by "/" and a number n, to indicate a whole subnet, i.e. all
1172 addresses which have the same value in the most significant n bits. In
1173 this form, the address may be followed by a plus sign ("+") to indicate
1174 that one address from the subnet is authorized, based on the ppp net‐
1175 work interface unit number in use. In this case, the host part of the
1176 address will be set to the unit number plus one.
1177 Thus a secrets file contains both secrets for use in authenticating
1179 other hosts, plus secrets which we use for authenticating ourselves to
1180 others. When pppd is authenticating the peer (checking the peer's
1181 identity), it chooses a secret with the peer's name in the first field
1182 and the name of the local system in the second field. The name of the
1183 local system defaults to the hostname, with the domain name appended if
1184 the domain option is used. This default can be overridden with the
1185 name option, except when the usehostname option is used. (For EAP
1186 SRP-SHA1, see the srp-entry(8) utility for generating proper validator
1187 entries to be used in the "secret" field.)
1188 When pppd is choosing a secret to use in authenticating itself to the
1190 peer, it first determines what name it is going to use to identify
1191 itself to the peer. This name can be specified by the user with the
1192 user option. If this option is not used, the name defaults to the name
1193 of the local system, determined as described in the previous paragraph.
1194 Then pppd looks for a secret with this name in the first field and the
1195 peer's name in the second field. Pppd will know the name of the peer
1196 if CHAP or EAP authentication is being used, because the peer will have
1197 sent it in the challenge packet. However, if PAP is being used, pppd
1198 will have to determine the peer's name from the options specified by
1199 the user. The user can specify the peer's name directly with the
1200 remotename option. Otherwise, if the remote IP address was specified
1201 by a name (rather than in numeric form), that name will be used as the
1202 peer's name. Failing that, pppd will use the null string as the peer's
1203 name.
1204 When authenticating the peer with PAP, the supplied password is first
1206 compared with the secret from the secrets file. If the password
1207 doesn't match the secret, the password is encrypted using crypt() and
1208 checked against the secret again. Thus secrets for authenticating the
1209 peer can be stored in encrypted form if desired. If the papcrypt
1210 option is given, the first (unencrypted) comparison is omitted, for
1211 better security.
1212 Furthermore, if the login option was specified, the username and pass‐
1214 word are also checked against the system password database. Thus, the
1215 system administrator can set up the pap-secrets file to allow PPP
1216 access only to certain users, and to restrict the set of IP addresses
1217 that each user can use. Typically, when using the login option, the
1218 secret in /etc/ppp/pap-secrets would be "", which will match any pass‐
1219 word supplied by the peer. This avoids the need to have the same
1220 secret in two places.
1221 Authentication must be satisfactorily completed before IPCP (or any
1223 other Network Control Protocol) can be started. If the peer is
1224 required to authenticate itself, and fails to do so, pppd will termi‐
1225 nated the link (by closing LCP). If IPCP negotiates an unacceptable IP
1226 address for the remote host, IPCP will be closed. IP packets can only
1227 be sent or received when IPCP is open.
1228 In some cases it is desirable to allow some hosts which can't authenti‐
1230 cate themselves to connect and use one of a restricted set of IP
1231 addresses, even when the local host generally requires authentication.
1232 If the peer refuses to authenticate itself when requested, pppd takes
1233 that as equivalent to authenticating with PAP using the empty string
1234 for the username and password. Thus, by adding a line to the
1235 pap-secrets file which specifies the empty string for the client and
1236 password, it is possible to allow restricted access to hosts which
1237 refuse to authenticate themselves.
1238
1240 When IPCP negotiation is completed successfully, pppd will inform the
1241 kernel of the local and remote IP addresses for the ppp interface.
1242 This is sufficient to create a host route to the remote end of the
1243 link, which will enable the peers to exchange IP packets. Communica‐
1244 tion with other machines generally requires further modification to
1245 routing tables and/or ARP (Address Resolution Protocol) tables. In
1246 most cases the defaultroute and/or proxyarp options are sufficient for
1247 this, but in some cases further intervention is required. The
1248 /etc/ppp/ip-up script can be used for this.
1249 Sometimes it is desirable to add a default route through the remote
1251 host, as in the case of a machine whose only connection to the Internet
1252 is through the ppp interface. The defaultroute option causes pppd to
1253 create such a default route when IPCP comes up, and delete it when the
1254 link is terminated.
1255 In some cases it is desirable to use proxy ARP, for example on a server
1257 machine connected to a LAN, in order to allow other hosts to communi‐
1258 cate with the remote host. The proxyarp option causes pppd to look for
1259 a network interface on the same subnet as the remote host (an interface
1260 supporting broadcast and ARP, which is up and not a point-to-point or
1261 loopback interface). If found, pppd creates a permanent, published ARP
1262 entry with the IP address of the remote host and the hardware address
1263 of the network interface found.
1264 When the demand option is used, the interface IP addresses have already
1266 been set at the point when IPCP comes up. If pppd has not been able to
1267 negotiate the same addresses that it used to configure the interface
1268 (for example when the peer is an ISP that uses dynamic IP address
1269 assignment), pppd has to change the interface IP addresses to the nego‐
1270 tiated addresses. This may disrupt existing connections, and the use
1271 of demand dialling with peers that do dynamic IP address assignment is
1272 not recommended.
1273
1275 Multilink PPP provides the capability to combine two or more PPP links
1276 between a pair of machines into a single `bundle', which appears as a
1277 single virtual PPP link which has the combined bandwidth of the indi‐
1278 vidual links. Currently, multilink PPP is only supported under Linux.
1279 Pppd detects that the link it is controlling is connected to the same
1281 peer as another link using the peer's endpoint discriminator and the
1282 authenticated identity of the peer (if it authenticates itself). The
1283 endpoint discriminator is a block of data which is hopefully unique for
1284 each peer. Several types of data can be used, including locally-
1285 assigned strings of bytes, IP addresses, MAC addresses, randomly
1286 strings of bytes, or E-164 phone numbers. The endpoint discriminator
1287 sent to the peer by pppd can be set using the endpoint option.
1288 In some circumstances the peer may send no endpoint discriminator or a
1290 non-unique value. The bundle option adds an extra string which is
1291 added to the peer's endpoint discriminator and authenticated identity
1292 when matching up links to be joined together in a bundle. The bundle
1293 option can also be used to allow the establishment of multiple bundles
1294 between the local system and the peer. Pppd uses a TDB database in
1295 /var/run/pppd2.tdb to match up links.
1296 Assuming that multilink is enabled and the peer is willing to negotiate
1298 multilink, then when pppd is invoked to bring up the first link to the
1299 peer, it will detect that no other link is connected to the peer and
1300 create a new bundle, that is, another ppp network interface unit. When
1301 another pppd is invoked to bring up another link to the peer, it will
1302 detect the existing bundle and join its link to it.
1303 If the first link terminates (for example, because of a hangup or a
1305 received LCP terminate-request) the bundle is not destroyed unless
1306 there are no other links remaining in the bundle. Rather than exiting,
1307 the first pppd keeps running after its link terminates, until all the
1308 links in the bundle have terminated. If the first pppd receives a
1309 SIGTERM or SIGINT signal, it will destroy the bundle and send a SIGHUP
1310 to the pppd processes for each of the links in the bundle. If the
1311 first pppd receives a SIGHUP signal, it will terminate its link but not
1312 the bundle.
1313 Note: demand mode is not currently supported with multilink.
1315
1317 The following examples assume that the /etc/ppp/options file contains
1318 the auth option (as in the default /etc/ppp/options file in the ppp
1319 distribution).
1320 Probably the most common use of pppd is to dial out to an ISP. This
1322 can be done with a command such as
1323 pppd call isp
1325 where the /etc/ppp/peers/isp file is set up by the system administrator
1327 to contain something like this:
1328 ttyS0 19200 crtscts
1330 connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
1331 noauth
1332 In this example, we are using chat to dial the ISP's modem and go
1334 through any logon sequence required. The /etc/ppp/chat-isp file con‐
1335 tains the script used by chat; it could for example contain something
1336 like this:
1337 ABORT "NO CARRIER"
1339 ABORT "NO DIALTONE"
1340 ABORT "ERROR"
1341 ABORT "NO ANSWER"
1342 ABORT "BUSY"
1343 ABORT "Username/Password Incorrect"
1344 "" "at"
1345 OK "at&d0&c1"
1346 OK "atdt2468135"
1347 "name:" "^Umyuserid"
1348 "word:" "\qmypassword"
1349 "ispts" "\q^Uppp"
1350 "~-^Uppp-~"
1351 See the chat(8) man page for details of chat scripts.
1353 Pppd can also be used to provide a dial-in ppp service for users. If
1355 the users already have login accounts, the simplest way to set up the
1356 ppp service is to let the users log in to their accounts and run pppd
1357 (installed setuid-root) with a command such as
1358 pppd proxyarp
1360 To allow a user to use the PPP facilities, you need to allocate an IP
1362 address for that user's machine and create an entry in
1363 /etc/ppp/pap-secrets, /etc/ppp/chap-secrets, or /etc/ppp/srp-secrets
1364 (depending on which authentication method the PPP implementation on the
1365 user's machine supports), so that the user's machine can authenticate
1366 itself. For example, if Joe has a machine called "joespc" that is to
1367 be allowed to dial in to the machine called "server" and use the IP
1368 address joespc.my.net, you would add an entry like this to
1369 /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:
1370 joespc server "joe's secret" joespc.my.net
1372 (See srp-entry(8) for a means to generate the server's entry when
1374 SRP-SHA1 is in use.) Alternatively, you can create a username called
1375 (for example) "ppp", whose login shell is pppd and whose home directory
1376 is /etc/ppp. Options to be used when pppd is run this way can be put
1377 in /etc/ppp/.ppprc.
1378 If your serial connection is any more complicated than a piece of wire,
1380 you may need to arrange for some control characters to be escaped. In
1381 particular, it is often useful to escape XON (^Q) and XOFF (^S), using
1382 asyncmap a0000. If the path includes a telnet, you probably should
1383 escape ^] as well (asyncmap 200a0000). If the path includes an rlogin,
1384 you will need to use the escape ff option on the end which is running
1385 the rlogin client, since many rlogin implementations are not transpar‐
1386 ent; they will remove the sequence [0xff, 0xff, 0x73, 0x73, followed by
1387 any 8 bytes] from the stream.
1388
1390 Messages are sent to the syslog daemon using facility LOG_DAEMON.
1391 (This can be overridden by recompiling pppd with the macro LOG_PPP
1392 defined as the desired facility.) See the syslog(8) documentation for
1393 details of where the syslog daemon will write the messages. On most
1394 systems, the syslog daemon uses the /etc/syslog.conf file to specify
1395 the destination(s) for syslog messages. You may need to edit that file
1396 to suit.
1397 The debug option causes the contents of all control packets sent or
1399 received to be logged, that is, all LCP, PAP, CHAP, EAP, or IPCP pack‐
1400 ets. This can be useful if the PPP negotiation does not succeed or if
1401 authentication fails. If debugging is enabled at compile time, the
1402 debug option also causes other debugging messages to be logged.
1403 Debugging can also be enabled or disabled by sending a SIGUSR1 signal
1405 to the pppd process. This signal acts as a toggle.
1406
1408 The exit status of pppd is set to indicate whether any error was
1409 detected, or the reason for the link being terminated. The values used
1410 are:
1411 0 Pppd has detached, or otherwise the connection was successfully
1413 established and terminated at the peer's request.
1414 1 An immediately fatal error of some kind occurred, such as an
1416 essential system call failing, or running out of virtual memory.
1417 2 An error was detected in processing the options given, such as
1419 two mutually exclusive options being used.
1420 3 Pppd is not setuid-root and the invoking user is not root.
1422 4 The kernel does not support PPP, for example, the PPP kernel
1424 driver is not included or cannot be loaded.
1425 5 Pppd terminated because it was sent a SIGINT, SIGTERM or SIGHUP
1427 signal.
1428 6 The serial port could not be locked.
1430 7 The serial port could not be opened.
1432 8 The connect script failed (returned a non-zero exit status).
1434 9 The command specified as the argument to the pty option could
1436 not be run.
1437 10 The PPP negotiation failed, that is, it didn't reach the point
1439 where at least one network protocol (e.g. IP) was running.
1440 11 The peer system failed (or refused) to authenticate itself.
1442 12 The link was established successfully and terminated because it
1444 was idle.
1445 13 The link was established successfully and terminated because the
1447 connect time limit was reached.
1448 14 Callback was negotiated and an incoming call should arrive
1450 shortly.
1451 15 The link was terminated because the peer is not responding to
1453 echo requests.
1454 16 The link was terminated by the modem hanging up.
1456 17 The PPP negotiation failed because serial loopback was detected.
1458 18 The init script failed (returned a non-zero exit status).
1460 19 We failed to authenticate ourselves to the peer.
1462
1464 Pppd invokes scripts at various stages in its processing which can be
1465 used to perform site-specific ancillary processing. These scripts are
1466 usually shell scripts, but could be executable code files instead.
1467 Pppd does not wait for the scripts to finish (except for the ip-pre-up
1468 script). The scripts are executed as root (with the real and effective
1469 user-id set to 0), so that they can do things such as update routing
1470 tables or run privileged daemons. Be careful that the contents of
1471 these scripts do not compromise your system's security. Pppd runs the
1472 scripts with standard input, output and error redirected to /dev/null,
1473 and with an environment that is empty except for some environment vari‐
1474 ables that give information about the link. The environment variables
1475 that pppd sets are:
1476 DEVICE The name of the serial tty device being used.
1478 IFNAME The name of the network interface being used.
1480 IPLOCAL
1482 The IP address for the local end of the link. This is only set
1483 when IPCP has come up.
1484 IPREMOTE
1486 The IP address for the remote end of the link. This is only set
1487 when IPCP has come up.
1488 PEERNAME
1490 The authenticated name of the peer. This is only set if the
1491 peer authenticates itself.
1492 SPEED The baud rate of the tty device.
1494 ORIG_UID
1496 The real user-id of the user who invoked pppd.
1497 PPPLOGNAME
1499 The username of the real user-id that invoked pppd. This is
1500 always set.
1501 For the ip-down and auth-down scripts, pppd also sets the following
1503 variables giving statistics for the connection:
1504 CONNECT_TIME
1506 The number of seconds from when the PPP negotiation started
1507 until the connection was terminated.
1508 BYTES_SENT
1510 The number of bytes sent (at the level of the serial port) dur‐
1511 ing the connection.
1512 BYTES_RCVD
1514 The number of bytes received (at the level of the serial port)
1515 during the connection.
1516 LINKNAME
1518 The logical name of the link, set with the linkname option.
1519 DNS1 If the peer supplies DNS server addresses, this variable is set
1521 to the first DNS server address supplied.
1522 DNS2 If the peer supplies DNS server addresses, this variable is set
1524 to the second DNS server address supplied.
1525 Pppd invokes the following scripts, if they exist. It is not an error
1527 if they don't exist.
1528 /etc/ppp/auth-up
1530 A program or script which is executed after the remote system
1531 successfully authenticates itself. It is executed with the
1532 parameters
1533 interface-name peer-name user-name tty-device speed
1535 Note that this script is not executed if the peer doesn't
1537 authenticate itself, for example when the noauth option is used.
1538 /etc/ppp/auth-down
1540 A program or script which is executed when the link goes down,
1541 if /etc/ppp/auth-up was previously executed. It is executed in
1542 the same manner with the same parameters as /etc/ppp/auth-up.
1543 /etc/ppp/ip-pre-up
1545 A program or script which is executed just before the ppp net‐
1546 work interface is brought up. It is executed with the same
1547 parameters as the ip-up script (below). At this point the
1548 interface exists and has IP addresses assigned but is still
1549 down. This can be used to add firewall rules before any IP
1550 traffic can pass through the interface. Pppd will wait for this
1551 script to finish before bringing the interface up, so this
1552 script should run quickly.
1553 /etc/ppp/ip-up
1555 A program or script which is executed when the link is available
1556 for sending and receiving IP packets (that is, IPCP has come
1557 up). It is executed with the parameters
1558 interface-name tty-device speed local-IP-address
1560 remote-IP-address ipparam
1561 /etc/ppp/ip-down
1563 A program or script which is executed when the link is no longer
1564 available for sending and receiving IP packets. This script can
1565 be used for undoing the effects of the /etc/ppp/ip-up and
1566 /etc/ppp/ip-pre-up scripts. It is invoked in the same manner
1567 and with the same parameters as the ip-up script.
1568 /etc/ppp/ipv6-up
1570 Like /etc/ppp/ip-up, except that it is executed when the link is
1571 available for sending and receiving IPv6 packets. It is executed
1572 with the parameters
1573 interface-name tty-device speed local-link-local-address
1575 remote-link-local-address ipparam
1576 /etc/ppp/ipv6-down
1578 Similar to /etc/ppp/ip-down, but it is executed when IPv6 pack‐
1579 ets can no longer be transmitted on the link. It is executed
1580 with the same parameters as the ipv6-up script.
1581 /etc/ppp/ipx-up
1583 A program or script which is executed when the link is available
1584 for sending and receiving IPX packets (that is, IPXCP has come
1585 up). It is executed with the parameters
1586 interface-name tty-device speed network-number
1588 local-IPX-node-address remote-IPX-node-address local-IPX-rout‐
1589 ing-protocol remote-IPX-routing-protocol local-IPX-router-name
1590 remote-IPX-router-name ipparam pppd-pid
1591 The local-IPX-routing-protocol and remote-IPX-routing-protocol
1593 field may be one of the following:
1594 NONE to indicate that there is no routing protocol
1596 RIP to indicate that RIP/SAP should be used
1597 NLSP to indicate that Novell NLSP should be used
1598 RIP NLSP to indicate that both RIP/SAP and NLSP should be used
1599 /etc/ppp/ipx-down
1601 A program or script which is executed when the link is no longer
1602 available for sending and receiving IPX packets. This script
1603 can be used for undoing the effects of the /etc/ppp/ipx-up
1604 script. It is invoked in the same manner and with the same
1605 parameters as the ipx-up script.
1606
1608 /var/run/pppn.pid (BSD or Linux), /etc/ppp/pppn.pid (others)
1609 Process-ID for pppd process on ppp interface unit n.
1610 /var/run/ppp-name.pid (BSD or Linux),
1612 /etc/ppp/ppp-name.pid (others) Process-ID for pppd process for
1613 logical link name (see the linkname option).
1614 /var/run/pppd2.tdb
1616 Database containing information about pppd processes, interfaces
1617 and links, used for matching links to bundles in multilink oper‐
1618 ation. May be examined by external programs to obtain informa‐
1619 tion about running pppd instances, the interfaces and devices
1620 they are using, IP address assignments, etc.
1621 /etc/ppp/pap-secrets Usernames, passwords and IP addresses for
1622 PAP authentication. This file should be owned by root and not
1623 readable or writable by any other user. Pppd will log a warning
1624 if this is not the case.
1625 /etc/ppp/chap-secrets
1627 Names, secrets and IP addresses for CHAP/MS-CHAP/MS-CHAPv2
1628 authentication. As for /etc/ppp/pap-secrets, this file should
1629 be owned by root and not readable or writable by any other user.
1630 Pppd will log a warning if this is not the case.
1631 /etc/ppp/srp-secrets
1633 Names, secrets, and IP addresses for EAP authentication. As for
1634 /etc/ppp/pap-secrets, this file should be owned by root and not
1635 readable or writable by any other user. Pppd will log a warning
1636 if this is not the case.
1637 ~/.ppp_pseudonym
1639 Saved client-side SRP-SHA1 pseudonym. See the srp-use-pseudonym
1640 option for details.
1641 /etc/ppp/options
1643 System default options for pppd, read before user default
1644 options or command-line options.
1645 ~/.ppprc
1647 User default options, read before /etc/ppp/options.ttyname.
1648 /etc/ppp/options.ttyname
1650 System default options for the serial port being used, read
1651 after ~/.ppprc. In forming the ttyname part of this filename,
1652 an initial /dev/ is stripped from the port name (if present),
1653 and any slashes in the remaining part are converted to dots.
1654 /etc/ppp/peers
1656 A directory containing options files which may contain privi‐
1657 leged options, even if pppd was invoked by a user other than
1658 root. The system administrator can create options files in this
1659 directory to permit non-privileged users to dial out without
1660 requiring the peer to authenticate, but only to certain trusted
1661 peers.
1662
1664 chat(8), pppstats(8)
1665 RFC1144
1667 Jacobson, V. Compressing TCP/IP headers for low-speed serial
1668 links. February 1990.
1669 RFC1321
1671 Rivest, R. The MD5 Message-Digest Algorithm. April 1992.
1672 RFC1332
1674 McGregor, G. PPP Internet Protocol Control Protocol (IPCP).
1675 May 1992.
1676 RFC1334
1678 Lloyd, B.; Simpson, W.A. PPP authentication protocols. October
1679 1992.
1680 RFC1661
1682 Simpson, W.A. The Point-to-Point Protocol (PPP). July 1994.
1683 RFC1662
1685 Simpson, W.A. PPP in HDLC-like Framing. July 1994.
1686 RFC2284
1688 Blunk, L.; Vollbrecht, J., PPP Extensible Authentication Proto‐
1689 col (EAP). March 1998.
1690 RFC2472
1692 Haskin, D. IP Version 6 over PPP December 1998.
1693 RFC2945
1695 Wu, T., The SRP Authentication and Key Exchange System September
1696 2000.
1697 draft-ietf-pppext-eap-srp-03.txt
1699 Carlson, J.; et al., EAP SRP-SHA1 Authentication Protocol. July
1700 2001.
1701
1703 Some limited degree of control can be exercised over a running pppd
1704 process by sending it a signal from the list below.
1705 SIGINT, SIGTERM
1707 These signals cause pppd to terminate the link (by closing LCP),
1708 restore the serial device settings, and exit. If a connector or
1709 disconnector process is currently running, pppd will send the
1710 same signal to its process group, so as to terminate the connec‐
1711 tor or disconnector process.
1712 SIGHUP This signal causes pppd to terminate the link, restore the
1714 serial device settings, and close the serial device. If the
1715 persist or demand option has been specified, pppd will try to
1716 reopen the serial device and start another connection (after the
1717 holdoff period). Otherwise pppd will exit. If this signal is
1718 received during the holdoff period, it causes pppd to end the
1719 holdoff period immediately. If a connector or disconnector
1720 process is running, pppd will send the same signal to its
1721 process group.
1722 SIGUSR1
1724 This signal toggles the state of the debug option.
1725 SIGUSR2
1727 This signal causes pppd to renegotiate compression. This can be
1728 useful to re-enable compression after it has been disabled as a
1729 result of a fatal decompression error. (Fatal decompression
1730 errors generally indicate a bug in one or other implementation.)
1731
1734 Paul Mackerras (paulus@samba.org), based on earlier work by Drew
1735 Perkins, Brad Clements, Karl Fox, Greg Christy, and Brad Parker.
1736
1739 Pppd is copyrighted and made available under conditions which provide
1740 that it may be copied and used in source or binary forms provided that
1741 the conditions listed below are met. Portions of pppd are covered by
1742 the following copyright notices:
1743 Copyright (c) 1984-2000 Carnegie Mellon University. All rights
1745 reserved.
1746 Copyright (c) 1993-2004 Paul Mackerras. All rights reserved.
1747 Copyright (c) 1995 Pedro Roque Marques. All rights reserved.
1748 Copyright (c) 1995 Eric Rosenquist. All rights reserved.
1749 Copyright (c) 1999 Tommi Komulainen. All rights reserved.
1750 Copyright (C) Andrew Tridgell 1999
1751 Copyright (c) 2000 by Sun Microsystems, Inc. All rights reserved.
1752 Copyright (c) 2001 by Sun Microsystems, Inc. All rights reserved.
1753 Copyright (c) 2002 Google, Inc. All rights reserved.
1754 The copyright notices contain the following statements.
1756 Redistribution and use in source and binary forms, with or without mod‐
1758 ification, are permitted provided that the following conditions are
1759 met:
1760 1. Redistributions of source code must retain the above copyright
1762 notice, this list of conditions and the following disclaimer.
1763 2. Redistributions in binary form must reproduce the above copyright
1765 notice, this list of conditions and the following disclaimer in
1766 the documentation and/or other materials provided with the
1767 distribution.
1768 3. The name "Carnegie Mellon University" must not be used to
1770 endorse or promote products derived from this software without
1771 prior written permission. For permission or any legal
1772 details, please contact
1773 Office of Technology Transfer
1774 Carnegie Mellon University
1775 5000 Forbes Avenue
1776 Pittsburgh, PA 15213-3890
1777 (412) 268-4387, fax: (412) 268-7395
1778 tech-transfer@andrew.cmu.edu
1779 3b. The name(s) of the authors of this software must not be used to
1781 endorse or promote products derived from this software without
1782 prior written permission.
1783 4. Redistributions of any form whatsoever must retain the following
1785 acknowledgments:
1786 "This product includes software developed by Computing Services
1787 at Carnegie Mellon University (http://www.cmu.edu/computing/)."
1788 "This product includes software developed by Paul Mackerras
1789 <paulus@samba.org>".
1790 "This product includes software developed by Pedro Roque Marques
1791 <pedro_m@yahoo.com>".
1792 "This product includes software developed by Tommi Komulainen
1793 <Tommi.Komulainen@iki.fi>".
1794 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
1796 SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FIT‐
1797 NESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE FOR ANY
1798 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
1799 RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
1800 CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
1801 CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
1802 THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
1804 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
1805 FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY SPECIAL, INDI‐
1806 RECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
1807 LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLI‐
1808 GENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH
1809 THE USE OR PERFORMANCE OF THIS SOFTWARE.
1810 PPPD(8)