1 .\" manual page [] for pppd 2.0
2 .\" $Id: pppd.8,v 1.4 1994/05/09 02:40:39 paulus Exp $
4 .\" SS subsection heading
6 .\" IP indented paragraph
10 pppd \- Point to Point Protocol daemon
22 The Point-to-Point Protocol (PPP) provides a method for transmitting
23 datagrams over serial point-to-point links. PPP
24 is composed of three parts: a method for encapsulating datagrams over
25 serial links, an extensible Link Control Protocol (LCP), and
26 a family of Network Control Protocols (NCP) for establishing
27 and configuring different network-layer protocols.
29 The encapsulation scheme is provided by driver code in the kernel.
31 provides the basic LCP, authentication support, and an
32 NCP for establishing and configuring the Internet Protocol (IP)
33 (called the IP Control Protocol, IPCP).
34 .SH FREQUENTLY USED OPTIONS
37 Communicate over the named device. The string "/dev/"
38 is prepended if necessary. If no device name is given,
40 will use the controlling terminal, and will not fork to put itself in
44 Set the baud rate to <speed>. On systems such as 4.4BSD and NetBSD,
45 any speed can be specified. Other systems (e.g. SunOS) allow only a
46 limited set of speeds.
49 Set the async character map to <map>.
50 This map describes which control characters cannot be successfully
51 received over the serial line.
53 will ask the peer to send these characters as a 2-byte escape sequence.
54 The argument is a 32 bit hex number
55 with each bit representing a character to escape.
56 Bit 0 (00000001) represents the character 0x00;
57 bit 31 (80000000) represents the character 0x1f or ^_.
58 If multiple \fBasyncmap\fR options are
59 given, the values are ORed together.
60 If no \fBasyncmap\fR option is given, no async character map will be
61 negotiated for the receive direction; the peer will then escape
62 \fIall\fR control characters.
65 Require the peer to authenticate itself before allowing network
66 packets to be sent or received.
69 Use the executable or shell command specified by \fI<p>\fR to set up the
70 serial line. This script would typically use the "chat" program to
71 dial the modem and start the remote ppp session.
74 Use hardware flow control (i.e. RTS/CTS) to control the flow of data on
78 Add a default route to the system routing tables, using the peer as
79 the gateway, when IPCP negotiation is successfully completed.
80 This entry is removed when the PPP connection is broken.
83 Run the executable or shell command specified by \fI<p>\fR after
84 \fIpppd\fR has terminated the link. This script could, for example,
85 issue commands to the modem to cause it to hang up.
87 .B escape \fIxx,yy,...
88 Specifies that certain characters should be escaped on transmission
89 (regardless of whether the peer requests them to be escaped with its
90 async control character map). The characters to be escaped are
91 specified as a list of hex numbers separated by commas. Note that
92 almost any character can be specified for the \fBescape\fR option,
93 unlike the \fBasyncmap\fR option which only allows control characters
94 to be specified. The characters which may not be escaped are those
95 with hex values 0x20 - 0x3f or 0x5e.
98 Read options from file <f> (the format is described below).
101 Specifies that \fIpppd\fR should use a UUCP-style lock on the serial
102 device to ensure exclusive access to the device.
105 Set the MRU [Maximum Receive Unit] value to <n> for negotiation.
107 will ask the peer to send packets of no more than <n> bytes.
108 The minimum MRU value is 128.
109 The default MRU value is 1500. A value of 296 is recommended for slow
110 links (40 bytes for TCP/IP header + 256 bytes of data).
113 Set the interface netmask to <n>, a 32 bit netmask in "decimal dot" notation
114 (e.g. 255.255.255.0).
117 Enables the "passive" option in the LCP. With this option,
119 will attempt to initiate a connection; if no reply is received from
122 will then just wait passively for a valid LCP packet from the peer
123 (instead of exiting, as it does without this option).
128 will not transmit LCP packets to initiate a connection until a valid
129 LCP packet is received from the peer (as for the "passive" option with
130 old versions of \fIpppd\fR).
133 .I <local_IP_address>\fB:\fI<remote_IP_address>
134 Set the local and/or remote interface IP addresses. Either one may be
135 omitted. The IP addresses can be specified with a host name or in
136 decimal dot notation (e.g. 150.234.56.78). The default local
137 address is the (first) IP address of the system (unless the
139 option is given). The remote address will be obtained from the peer
140 if not specified in any option. Thus, in simple cases, this option is
142 If a local and/or remote IP address is specified with this option,
144 will not accept a different value from the peer in the IPCP
145 negotiation, unless the
148 .B ipcp-accept-remote
149 options are given, respectively.
152 Don't request or allow negotiation of any options for LCP and IPCP (use
156 Disable Address/Control compression negotiation (use default, i.e.
157 address/control field disabled).
160 Disable asyncmap negotiation (use the default asyncmap, i.e. escape
161 all control characters).
168 Increase debugging level (same as the \fBdebug\fR option).
171 Don't fork to become a background process (otherwise
173 will do so if a serial device is specified).
176 Disable IP address negotiation (with this option, the remote IP
177 address must be specified with an option on the command line or in an
181 Disable magic number negotiation. With this option,
183 cannot detect a looped-back line.
186 Disable MRU [Maximum Receive Unit] negotiation (use default, i.e. 1500).
194 Disable protocol field compression negotiation (use default, i.e.
195 protocol field compression disabled).
198 Agree to authenticate using PAP [Password Authentication Protocol] if
199 requested by the peer, and
200 use the data in file <p> for the user and password to send to the
201 peer. The file contains the remote user name, followed by a newline,
202 followed by the remote password, followed by a newline. This option
206 Require the peer to authenticate itself using PAP.
209 Don't agree to authenticate using PAP.
212 Require the peer to authenticate itself using CHAP [Cryptographic
213 Handshake Authentication Protocol] authentication.
216 Don't agree to authenticate using CHAP.
219 Disable negotiation of Van Jacobson style IP header compression (use
220 default, i.e. no compression).
223 Increase debugging level (same as \fB\-d\fR).
225 option is given, \fIpppd\fR will log the contents of all control
226 packets sent or received in a readable form. The packets are logged
227 through syslog with facility \fIdaemon\fR and level \fIdebug\fR. This
228 information can be directed to a file by setting up /etc/syslog.conf
229 appropriately (see syslog.conf(5)).
232 Append the domain name <d> to the local host name for authentication
233 purposes. For example, if gethostname() returns the name porsche, but the
234 fully qualified domain name is porsche.Quotron.COM, you would use the
235 domain option to set the domain name to Quotron.COM.
238 Use the modem control lines. On Ultrix, this option implies hardware
239 flow control, as for the \fBcrtscts\fR option. (This option is not fully
243 Enable debugging code in the kernel-level PPP driver. The argument
244 \fIn\fR is a number which is the sum of the following values: 1 to
245 enable general debug messages, 2 to request that the contents of
246 received packets be printed, and 4 to request that the contents of
247 transmitted packets be printed.
250 Don't use the modem control lines.
253 Set the MTU [Maximum Transmit Unit] value to \fI<n>\fR. Unless the
254 peer requests a smaller value via MRU negotiation, \fIpppd\fR will
255 request that the kernel networking code send data packets of no more
256 than \fIn\fR bytes through the PPP network interface.
259 Set the name of the local system for authentication purposes to <n>.
262 Set the user name to use for authenticating this machine with the peer
266 Enforce the use of the hostname as the name of the local system for
267 authentication purposes (overrides the
272 Set the assumed name of the remote system for authentication purposes
276 Add an entry to this system's ARP [Address Resolution Protocol] table
277 with the IP address of the peer and the Ethernet address of this
281 Use the system password database for authenticating the peer using
285 Disables the default behaviour when no local IP address is specified,
286 which is to determine (if possible) the local IP address from the
287 hostname. With this option, the peer will have to supply the local IP
288 address during IPCP negotiation (unless it specified explicitly on the
289 command line or in an options file).
291 .B lcp-restart \fI<n>
292 Set the LCP restart interval (retransmission timeout) to <n> seconds
295 .B lcp-max-terminate \fI<n>
296 Set the maximum number of LCP terminate-request transmissions to <n>
299 .B lcp-max-configure \fI<n>
300 Set the maximum number of LCP configure-request transmissions to <n>
303 .B lcp-max-failure \fI<n>
304 Set the maximum number of LCP configure-NAKs returned before starting
305 to send configure-Rejects instead to <n> (default 10).
307 .B ipcp-restart \fI<n>
308 Set the IPCP restart interval (retransmission timeout) to <n> seconds
311 .B ipcp-max-terminate \fI<n>
312 Set the maximum number of IPCP terminate-request transmissions to <n>
315 .B ipcp-max-configure \fI<n>
316 Set the maximum number of IPCP configure-request transmissions to <n>
319 .B ipcp-max-failure \fI<n>
320 Set the maximum number of IPCP configure-NAKs returned before starting
321 to send configure-Rejects instead to <n> (default 10).
323 .B pap-restart \fI<n>
324 Set the PAP restart interval (retransmission timeout) to <n> seconds
327 .B pap-max-authreq \fI<n>
328 Set the maximum number of PAP authenticate-request transmissions to
331 .B chap-restart \fI<n>
332 Set the CHAP restart interval (retransmission timeout for challenges)
333 to <n> seconds (default 3).
335 .B chap-max-challenge \fI<n>
336 Set the maximum number of CHAP challenge transmissions to <n> (default
339 .B chap-interval \fI<n>
340 If this option is given,
342 will rechallenge the peer every <n> seconds.
347 will accept the peer's idea of our local IP address, even if the
348 local IP address was specified in an option.
350 .B ipcp-accept-remote
353 will accept the peer's idea of its (remote) IP address, even if the
354 remote IP address was specified in an option.
356 Options can be taken from files as well as the command line.
358 reads options from the files /etc/ppp/options and $HOME/.ppprc before
359 looking at the command line. An options file is parsed into a series
360 of words, delimited by whitespace. Whitespace can be included in a
361 word by enclosing the word in quotes ("). A backslash (\\) quotes the
362 following character. A hash (#) starts a comment, which continues
363 until the end of the line.
366 provides system administrators with sufficient access control that PPP
367 access to a server machine can be provided to legitimate users without
368 fear of compromising the security of the server or the network it's
369 on. In part this is provided by the /etc/ppp/options file, where the
370 administrator can place options to require authentication whenever
372 is run, and in part by the PAP and CHAP secrets files, where the
373 administrator can restrict the set of IP addresses which individual
376 The default behaviour of
378 is to agree to authenticate if requested, and to not
379 require authentication from the peer. However,
382 authenticate itself with a particular protocol if it has no secrets
383 which could be used to do so.
385 Authentication is based on secrets, which are selected from secrets
386 files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
387 Both secrets files have the same format, and both can store secrets
388 for several combinations of server (authenticating peer) and client
389 (peer being authenticated). Note that
392 and client, and that different protocols can be used in the two
393 directions if desired.
395 A secrets file is parsed into words as for a options file. A secret
396 is specified by a line containing at least 3 words, in the order
397 client, server, secret. Any following words on the same line are
398 taken to be a list of acceptable IP addresses for that client. If
399 there are only 3 words on the line, it is assumed that any IP address
400 is OK; to disallow all IP addresses, use "-". If the secret starts
401 with an `@', what follows is assumed to be the name of a file from
402 which to read the secret. A "*" as the client or server name matches
403 any name. When selecting a secret, \fIpppd\fR takes the best match, i.e.
404 the match with the fewest wildcards.
406 Thus a secrets file contains both secrets for use in authenticating
407 other hosts, plus secrets which we use for authenticating ourselves to
408 others. Which secret to use is chosen based on the names of the host
409 (the `local name') and its peer (the `remote name'). The local name
412 if the \fBusehostname\fR option is given,
413 then the local name is the hostname of this machine
414 (with the domain appended, if given)
416 else if the \fBname\fR option is given,
417 then use the argument of the first \fBname\fR option seen
419 else if the local IP address is specified with a hostname,
422 else use the hostname of this machine (with the domain appended, if given)
424 When authenticating ourselves using PAP, there is also a `username'
425 which is the local name by default, but can be set with the \fBuser\fR
426 option or the \fB+ua\fR option.
428 The remote name is set as follows:
430 if the \fBremotename\fR option is given,
431 then use the argument of the last \fBremotename\fR option seen
433 else if the remote IP address is specified with a hostname,
434 then use that host name
436 else the remote name is the null string "".
438 Secrets are selected from the PAP secrets file as follows:
441 For authenticating the peer, look for a secret with client ==
442 username specified in the PAP authenticate-request, and server ==
446 For authenticating ourselves to the peer, look for a secret with
447 client == our username, server == remote name.
449 When authenticating the peer with PAP, a secret of "" matches any
450 password supplied by the peer. If the password doesn't match the
451 secret, the password is encrypted using crypt() and checked against
452 the secret again; thus secrets for authenticating the peer can be
453 stored in encrypted form. If the \fBlogin\fR option was specified, the
454 username and password are also checked against the system password
455 database. Thus, the system administrator can set up the pap-secrets
456 file to allow PPP access only to certain users, and to restrict the
457 set of IP addresses that each user can use.
459 Secrets are selected from the CHAP secrets file as follows:
462 For authenticating the peer, look for a secret with client == name
463 specified in the CHAP-Response message, and server == local name.
466 For authenticating ourselves to the peer, look for a secret with
467 client == local name, and server == name specified in the
468 CHAP-Challenge message.
470 Authentication must be satisfactorily completed before IPCP (or any
471 other Network Control Protocol) can be started. If authentication
472 fails, \fIpppd\fR will terminated the link (by closing LCP). If IPCP
473 negotiates an unacceptable IP address for the remote host, IPCP will
474 be closed. IP packets can only be sent or received when IPCP is open.
476 In some cases it is desirable to allow some hosts which can't
477 authenticate themselves to connect and use one of a restricted set of
478 IP addresses, even when the local host generally requires
479 authentication. If the peer refuses to authenticate itself when
480 requested, \fIpppd\fR takes that as equivalent to authenticating with
481 PAP using the empty string for the username and password. Thus, by
482 adding a line to the pap-secrets file which specifies the empty string
483 for the client and password, it is possible to allow restricted access
484 to hosts which refuse to authenticate themselves.
487 When IPCP negotiation is completed successfully,
489 will inform the kernel of the local and remote IP addresses for the
490 ppp interface. This is sufficient to create a
491 host route to the remote end of the link, which will enable the peers
492 to exchange IP packets. Communication with other machines generally
493 requires further modification to routing tables and/or ARP (Address
494 Resolution Protocol) tables. In some cases this will be done
495 automatically through the actions of the \fIrouted\fR or \fIgated\fR
496 daemons, but in most cases some further intervention is required.
498 Sometimes it is desirable
499 to add a default route through the remote host, as in the case of a
500 machine whose only connection to the Internet is through the ppp
501 interface. The \fBdefaultroute\fR option causes \fIpppd\fR to create such a
502 default route when IPCP comes up, and delete it when the link is
505 In some cases it is desirable to use proxy ARP, for example on a
506 server machine connected to a LAN, in order to allow other hosts to
507 communicate with the remote host. The \fBproxyarp\fR option causes \fIpppd\fR
508 to look for a network interface on the same subnet as the remote host
509 (an interface supporting broadcast and ARP, which is up and not a
510 point-to-point or loopback interface). If found, \fIpppd\fR creates a
511 permanent, published ARP entry with the IP address of the remote host
512 and the hardware address of the network interface found.
515 In the simplest case, you can connect the serial ports of two machines
516 and issue a command like
518 pppd /dev/ttya 9600 passive
520 to each machine, assuming there is no \fIgetty\fR running on the
521 serial ports. If one machine has a \fIgetty\fR running, you can use
522 \fIkermit\fR or \fItip\fR on the other machine to log in to the first
523 machine and issue a command like
527 Then exit from the communications program (making sure the connection
528 isn't dropped), and issue a command like
532 The process of logging in to the other machine and starting \fIpppd\fR
533 can be automated by using the \fBconnect\fR option to run \fIchat\fR,
536 pppd /dev/ttya 38400 connect 'chat "" "" "login:" "username"
537 "Password:" "password" "% " "exec pppd passive"'
539 (Note however that running chat like this will leave the password
540 visible in the parameter list of pppd and chat.)
542 If your serial connection is any more complicated than a piece of
543 wire, you may need to arrange for some control characters to be
544 escaped. In particular, it is often useful to escape XON (^Q) and
545 XOFF (^S), using \fBasyncmap a0000\fR. If the path includes a telnet,
546 you probably should escape ^] as well (\fBasyncmap 200a0000\fR).
547 If the path includes an rlogin, you will need to use the \fBescape
548 ff\fR option on the end which is running the rlogin client, since many
549 rlogin implementations are not
550 transparent; they will remove the sequence [0xff, 0xff, 0x73, 0x73,
551 followed by any 8 bytes] from the stream.
554 Messages are sent to the syslog daemon using facility LOG_DAEMON.
555 (This can be overriden by recompiling \fIpppd\fR with the macro
556 LOG_PPP defined as the desired facility.) In order to see the error
557 and debug messages, you will need to edit your /etc/syslog.conf file
558 to direct the messages to the desired output device or file.
560 The \fBdebug\fR option causes the contents of all control packets sent
561 or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
562 This can be useful if the PPP negotiation does not succeed.
563 If debugging is enabled at compile time, the \fBdebug\fR option also
564 causes other debugging messages to be logged.
566 Debugging can also be enabled by sending a
570 Debugging may be disabled by sending a SIGUSR2 to the
575 .B /var/run/ppp\fIn\fB.pid \fR(BSD), \fB/etc/ppp/ppp\fIn\fB.pid \fR(SunOS)
576 Process-ID for \fIpppd\fR process on ppp interface unit \fIn\fR.
578 .B /etc/ppp/pap-secrets
579 Usernames, passwords and IP addresses for PAP authentication.
581 .B /etc/ppp/chap-secrets
582 Names, secrets and IP addresses for CHAP authentication.
585 System default options for
587 read before user default options or command-line options.
590 User default options, read before command-line options.
595 .I Compressing TCP/IP headers for low-speed serial links.
600 .I The MD5 Message-Digest Algorithm.
605 .I PPP Internet Protocol Control Protocol (IPCP).
609 Lloyd, B.; Simpson, W.A.
610 .I PPP authentication protocols.
615 .I The Point\-to\-Point Protocol (PPP).
620 .I PPP in HDLC Framing.
623 The following signals have the specified effect when sent to the
628 These signals cause \fIpppd\fR to terminate the link (by closing LCP),
629 restore the serial device settings, and exit.
632 Indicates that the physical layer has been disconnected. \fIpppd\fR
633 will attempt to restore the serial device settings (this may produce
634 error messages on Suns), and then exit.
636 The use of the modem control lines and the effects of the \fBmodem\fR
637 and \fBlocal\fR options are not well defined.
643 Brad Parker (brad@fcr.com),
644 Paul Mackerras (paulus@cs.anu.edu.au)
projects / ppp.git / blob