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PPPD(8)                     System Manager's Manual                    PPPD(8)



NAME
       pppd - Point-to-Point Protocol Daemon

SYNOPSIS
       pppd [ options ]

DESCRIPTION
       PPP is the protocol used for establishing internet links over dial-up
       modems, DSL connections, and many other types of point-to-point links.
       The pppd daemon works together with the kernel PPP driver to establish
       and maintain a PPP link with another system (called the peer) and to
       negotiate Internet Protocol (IP) addresses for each end of the link.
       Pppd can also authenticate the peer and/or supply authentication
       information to the peer.  PPP can be used with other network protocols
       besides IP, but such use is becoming increasingly rare.

FREQUENTLY USED OPTIONS
       ttyname
              Use the serial port called ttyname to communicate with the peer.
              If ttyname does not begin with a slash (/), the string "/dev/"
              is prepended to ttyname to form the name of the device to open.
              If no device name is given, or if the name of the terminal
              connected to the standard input is given, pppd will use that
              terminal, and will not fork to put itself in the background.  A
              value for this option from a privileged source cannot be
              overridden by a non-privileged user.

       speed  An option that is a decimal number is taken as the desired baud
              rate for the serial device.  On systems such as 4.4BSD and
              NetBSD, any speed can be specified.  Other systems (e.g. Linux,
              SunOS) only support the commonly-used baud rates.

       asyncmap map
              This option sets the Async-Control-Character-Map (ACCM) for this
              end of the link.  The ACCM is a set of 32 bits, one for each of
              the ASCII control characters with values from 0 to 31, where a 1
              bit indicates that the corresponding control character should
              not be used in PPP packets sent to this system.  The map is
              encoded as a hexadecimal number (without a leading 0x) where the
              least significant bit (00000001) represents character 0 and the
              most significant bit (80000000) represents character 31.  Pppd
              will ask the peer to send these characters as a 2-byte escape
              sequence.  If multiple asyncmap options are given, the values
              are ORed together.  If no asyncmap option is given, the default
              is zero, so pppd will ask the peer not to escape any control
              characters.  To escape transmitted characters, use the escape
              option.

       auth   Require the peer to authenticate itself before allowing network
              packets to be sent or received.  This option is the default if
              the system has a default route.  If neither this option nor the
              noauth option is specified, pppd will only allow the peer to use
              IP addresses to which the system does not already have a route.

       call name
              Read additional options from the file /etc/ppp/peers/name.  This
              file may contain privileged options, such as noauth, even if
              pppd is not being run by root.  The name string may not begin
              with / or include .. as a pathname component.  The format of the
              options file is described below.

       connect script
              Usually there is something which needs to be done to prepare the
              link before the PPP protocol can be started; for instance, with
              a dial-up modem, commands need to be sent to the modem to dial
              the appropriate phone number.  This option specifies an command
              for pppd to execute (by passing it to a shell) before attempting
              to start PPP negotiation.  The chat (8) program is often useful
              here, as it provides a way to send arbitrary strings to a modem
              and respond to received characters.  A value for this option
              from a privileged source cannot be overridden by a non-
              privileged user.

       crtscts
              Specifies that pppd should set the serial port to use hardware
              flow control using the RTS and CTS signals in the RS-232
              interface.  If neither the crtscts, the nocrtscts, the cdtrcts
              nor the nocdtrcts option is given, the hardware flow control
              setting for the serial port is left unchanged.  Some serial
              ports (such as Macintosh serial ports) lack a true RTS output.
              Such serial ports use this mode to implement unidirectional flow
              control. The serial port will suspend transmission when
              requested by the modem (via CTS) but will be unable to request
              the modem to stop sending to the computer. This mode retains the
              ability to use DTR as a modem control line.

       defaultroute
              Add a default route to the system routing tables, using the peer
              as the gateway, when IPCP negotiation is successfully completed.
              This entry is removed when the PPP connection is broken.  This
              option is privileged if the nodefaultroute option has been
              specified.

       disconnect script
              Execute the command specified by script, by passing it to a
              shell, after pppd has terminated the link.  This command could,
              for example, issue commands to the modem to cause it to hang up
              if hardware modem control signals were not available.  The
              disconnect script is not run if the modem has already hung up.
              A value for this option from a privileged source cannot be
              overridden by a non-privileged user.

       escape xx,yy,...
              Specifies that certain characters should be escaped on
              transmission (regardless of whether the peer requests them to be
              escaped with its async control character map).  The characters
              to be escaped are specified as a list of hex numbers separated
              by commas.  Note that almost any character can be specified for
              the escape option, unlike the asyncmap option which only allows
              control characters to be specified.  The characters which may
              not be escaped are those with hex values 0x20 - 0x3f or 0x5e.

       file name
              Read options from file name (the format is described below).
              The file must be readable by the user who has invoked pppd.

       init script
              Execute the command specified by script, by passing it to a
              shell, to initialize the serial line.  This script would
              typically use the chat(8) program to configure the modem to
              enable auto answer.  A value for this option from a privileged
              source cannot be overridden by a non-privileged user.

       lock   Specifies that pppd should create a UUCP-style lock file for the
              serial device to ensure exclusive access to the device.  By
              default, pppd will not create a lock file.

       mru n  Set the MRU [Maximum Receive Unit] value to n. Pppd will ask the
              peer to send packets of no more than n bytes.  The value of n
              must be between 128 and 16384; the default is 1500.  A value of
              296 works well on very slow links (40 bytes for TCP/IP header +
              256 bytes of data).  Note that for the IPv6 protocol, the MRU
              must be at least 1280.

       mtu n  Set the MTU [Maximum Transmit Unit] value to n.  Unless the peer
              requests a smaller value via MRU negotiation, pppd will request
              that the kernel networking code send data packets of no more
              than n bytes through the PPP network interface.  Note that for
              the IPv6 protocol, the MTU must be at least 1280.

       passive
              Enables the "passive" option in the LCP.  With this option, pppd
              will attempt to initiate a connection; if no reply is received
              from the peer, pppd will then just wait passively for a valid
              LCP packet from the peer, instead of exiting, as it would
              without this option.

OPTIONS
       <local_IP_address>:<remote_IP_address>
              Set the local and/or remote interface IP addresses.  Either one
              may be omitted.  The IP addresses can be specified with a host
              name or in decimal dot notation (e.g. 150.234.56.78).  The
              default local address is the (first) IP address of the hostname
              of the system (unless the noipdefault option is given).  The
              remote address will be obtained from the peer if not specified
              in any option.  Thus, in simple cases, this option is not
              required.  If a local and/or remote IP address is specified with
              this option, pppd will not accept a different value from the
              peer in the IPCP negotiation, unless the ipcp-accept-local
              and/or ipcp-accept-remote options are given, respectively.

       ipv6 <local_interface_identifier>,<remote_interface_identifier>
              Set the local and/or remote 64-bit interface identifier. Either
              one may be omitted. The identifier must be specified in standard
              ascii notation of IPv6 addresses (e.g. ::dead:beef). If the
              ipv6cp-use-ipaddr option is given, the local identifier is the
              local IPv4 address (see above).  On systems which supports a
              unique persistent id, such as EUI-48 derived from the Ethernet
              MAC address, ipv6cp-use-persistent option can be used to replace
              the ipv6 <local>,<remote> option. Otherwise the identifier is
              randomized.

       active-filter-in filter-expression

       active-filter-out filter-expression
              Specifies an incoming and outgoing packet filter to be applied
              to data packets to determine which packets are to be regarded as
              link activity, and therefore reset the idle timer, or cause the
              link to be brought up in demand-dialing mode.  This option is
              useful in conjunction with the idle option if there are packets
              being sent or received regularly over the link (for example,
              routing information packets) which would otherwise prevent the
              link from ever appearing to be idle.  The filter-expression
              syntax is as described for tcpdump(8), except that qualifiers
              which are inappropriate for a PPP link, such as ether and arp,
              are not permitted.  Generally the filter expression should be
              enclosed in single-quotes to prevent whitespace in the
              expression from being interpreted by the shell. This option is
              currently only available under NetBSD, and then only if both the
              kernel and pppd were compiled with PPP_FILTER defined.

       allow-ip address(es)
              Allow peers to use the given IP address or subnet without
              authenticating themselves.  The parameter is parsed as for each
              element of the list of allowed IP addresses in the secrets files
              (see the AUTHENTICATION section below).

       allow-number number
              Allow peers to connect from the given telephone number.  A
              trailing `*' character will match all numbers beginning with the
              leading part.

       bsdcomp nr,nt
              Request that the peer compress packets that it sends, using the
              BSD-Compress scheme, with a maximum code size of nr bits, and
              agree to compress packets sent to the peer with a maximum code
              size of nt bits.  If nt is not specified, it defaults to the
              value given for nr.  Values in the range 9 to 15 may be used for
              nr and nt; larger values give better compression but consume
              more kernel memory for compression dictionaries.  Alternatively,
              a value of 0 for nr or nt disables compression in the
              corresponding direction.  Use nobsdcomp or bsdcomp 0 to disable
              BSD-Compress compression entirely.

       callback phone_number
              Request a call-back to the phone-number. This only works if the
              peer is speaking the Call Back Configuration Protocol. Don't put
              this into the main options file if you sometimes connect to
              servers that don't support it.

       cdtrcts
              Use a non-standard hardware flow control (i.e. DTR/CTS) to
              control the flow of data on the serial port.  If neither the
              crtscts, the nocrtscts, the cdtrcts nor the nocdtrcts option is
              given, the hardware flow control setting for the serial port is
              left unchanged.  Some serial ports (such as Macintosh serial
              ports) lack a true RTS output. Such serial ports use this mode
              to implement true bi-directional flow control. The sacrifice is
              that this flow control mode does not permit using DTR as a modem
              control line.

       chap-interval n
              If this option is given, pppd will rechallenge the peer every n
              seconds.

       chap-max-challenge n
              Set the maximum number of CHAP challenge transmissions to n
              (default 10).

       chap-restart n
              Set the CHAP restart interval (retransmission timeout for
              challenges) to n seconds (default 3).

       child-timeout n
              When exiting, wait for up to n seconds for any child processes
              (such as the command specified with the pty command) to exit
              before exiting.  At the end of the timeout, pppd will send a
              SIGTERM signal to any remaining child processes and exit.  A
              value of 0 means no timeout, that is, pppd will wait until all
              child processes have exited.

       connect-delay n
              Wait for up to n milliseconds after the connect script finishes
              for a valid PPP packet from the peer.  At the end of this time,
              or when a valid PPP packet is received from the peer, pppd will
              commence negotiation by sending its first LCP packet.  The
              default value is 1000 (1 second).  This wait period only applies
              if the connect or pty option is used.

       debug  Enables connection debugging facilities.  If this option is
              given, pppd will log the contents of all control packets sent or
              received in a readable form.  The packets are logged through
              syslog with facility daemon and level debug.  This information
              can be directed to a file by setting up /etc/syslog.conf
              appropriately (see syslog.conf(5)).

       default-asyncmap
              Disable asyncmap negotiation, forcing all control characters to
              be escaped for both the transmit and the receive direction.

       default-mru
              Disable MRU [Maximum Receive Unit] negotiation.  With this
              option, pppd will use the default MRU value of 1500 bytes for
              both the transmit and receive direction.

       deflate nr,nt
              Request that the peer compress packets that it sends, using the
              Deflate scheme, with a maximum window size of 2**nr bytes, and
              agree to compress packets sent to the peer with a maximum window
              size of 2**nt bytes.  If nt is not specified, it defaults to the
              value given for nr.  Values in the range 9 to 15 may be used for
              nr and nt; larger values give better compression but consume
              more kernel memory for compression dictionaries.  Alternatively,
              a value of 0 for nr or nt disables compression in the
              corresponding direction.  Use nodeflate or deflate 0 to disable
              Deflate compression entirely.  (Note: pppd requests Deflate
              compression in preference to BSD-Compress if the peer can do
              either.)

       demand Initiate the link only on demand, i.e. when data traffic is
              present.  With this option, the remote IP address must be
              specified by the user on the command line or in an options file.
              Pppd will initially configure the interface and enable it for IP
              traffic without connecting to the peer.  When traffic is
              available, pppd will connect to the peer and perform
              negotiation, authentication, etc.  When this is completed, pppd
              will commence passing data packets (i.e., IP packets) across the
              link.

              The demand option implies the persist option.  If this behavior
              is not desired, use the nopersist option after the demand
              option.  The idle and holdoff options are also useful in
              conjunction with the demand option.

       domain d
              Append the domain name d to the local host name for
              authentication purposes.  For example, if gethostname() returns
              the name porsche, but the fully qualified domain name is
              porsche.Quotron.COM, you could specify domain Quotron.COM.  Pppd
              would then use the name porsche.Quotron.COM for looking up
              secrets in the secrets file, and as the default name to send to
              the peer when authenticating itself to the peer.  This option is
              privileged.

       dryrun With the dryrun option, pppd will print out all the option
              values which have been set and then exit, after parsing the
              command line and options files and checking the option values,
              but before initiating the link.  The option values are logged at
              level info, and also printed to standard output unless the
              device on standard output is the device that pppd would be using
              to communicate with the peer.

       dump   With the dump option, pppd will print out all the option values
              which have been set.  This option is like the dryrun option
              except that pppd proceeds as normal rather than exiting.

       endpoint <epdisc>
              Sets the endpoint discriminator sent by the local machine to the
              peer during multilink negotiation to <epdisc>.  The default is
              to use the MAC address of the first ethernet interface on the
              system, if any, otherwise the IPv4 address corresponding to the
              hostname, if any, provided it is not in the multicast or
              locally-assigned IP address ranges, or the localhost address.
              The endpoint discriminator can be the string null or of the form
              type:value, where type is a decimal number or one of the strings
              local, IP, MAC, magic, or phone.  The value is an IP address in
              dotted-decimal notation for the IP type, or a string of bytes in
              hexadecimal, separated by periods or colons for the other types.
              For the MAC type, the value may also be the name of an ethernet
              or similar network interface.  This option is currently only
              available under Linux.

       eap-interval n
              If this option is given and pppd authenticates the peer with EAP
              (i.e., is the server), pppd will restart EAP authentication
              every n seconds.  For EAP SRP-SHA1, see also the srp-interval
              option, which enables lightweight rechallenge.

       eap-max-rreq n
              Set the maximum number of EAP Requests to which pppd will
              respond (as a client) without hearing EAP Success or Failure.
              (Default is 20.)

       eap-max-sreq n
              Set the maximum number of EAP Requests that pppd will issue (as
              a server) while attempting authentication.  (Default is 10.)

       eap-restart n
              Set the retransmit timeout for EAP Requests when acting as a
              server (authenticator).  (Default is 3 seconds.)

       eap-timeout n
              Set the maximum time to wait for the peer to send an EAP Request
              when acting as a client (authenticatee).  (Default is 20
              seconds.)

       hide-password
              When logging the contents of PAP packets, this option causes
              pppd to exclude the password string from the log.  This is the
              default.

       holdoff n
              Specifies how many seconds to wait before re-initiating the link
              after it terminates.  This option only has any effect if the
              persist or demand option is used.  The holdoff period is not
              applied if the link was terminated because it was idle.

       idle n Specifies that pppd should disconnect if the link is idle for n
              seconds.  The link is idle when no data packets (i.e. IP
              packets) are being sent or received.  Note: it is not advisable
              to use this option with the persist option without the demand
              option.  If the active-filter-in and/or active-filter-out
              options are given, data packets which are rejected by the
              specified activity filter also count as the link being idle.

       ipcp-accept-local
              With this option, pppd will accept the peer's idea of our local
              IP address, even if the local IP address was specified in an
              option.

       ipcp-accept-remote
              With this option, pppd will accept the peer's idea of its
              (remote) IP address, even if the remote IP address was specified
              in an option.

       ipcp-max-configure n
              Set the maximum number of IPCP configure-request transmissions
              to n (default 10).

       ipcp-max-failure n
              Set the maximum number of IPCP configure-NAKs returned before
              starting to send configure-Rejects instead to n (default 10).

       ipcp-max-terminate n
              Set the maximum number of IPCP terminate-request transmissions
              to n (default 3).

       ipcp-restart n
              Set the IPCP restart interval (retransmission timeout) to n
              seconds (default 3).

       ipparam string
              Provides an extra parameter to the ip-up, ip-pre-up and ip-down
              scripts.  If this option is given, the string supplied is given
              as the 6th parameter to those scripts.

       +ipv6  Enable IPv6CP negotiation and IPv6 communication.  It needs to
              be explicitly specified if you want IPv6CP.

       -ipv6  Disable IPv6CP negotiation and IPv6 communication.

       ipv6cp-accept-local
              With this option, pppd will accept the peer's idea of our local
              IPv6 address, even if the local IPv6 address was specified in an
              option.

       ipv6cp-use-ipaddr
              Use the local IPv4 address as the local interface address.

       ipv6cp-use-persistent
              Use uniquely-available persistent value for link local address
              (Solaris 2 only).

       ipv6cp-max-configure n
              Set the maximum number of IPv6CP configure-request transmissions
              to n (default 10).

       ipv6cp-max-failure n
              Set the maximum number of IPv6CP configure-NAKs returned before
              starting to send configure-Rejects instead to n (default 10).

       ipv6cp-max-terminate n
              Set the maximum number of IPv6CP terminate-request transmissions
              to n (default 3).

       ipv6cp-restart n
              Set the IPv6CP restart interval (retransmission timeout) to n
              seconds (default 3).

       ipx    Enable the IPXCP and IPX protocols.  This option is presently
              only supported under Linux, and only if your kernel has been
              configured to include IPX support.

       ipx-network n
              Set the IPX network number in the IPXCP configure request frame
              to n, a hexadecimal number (without a leading 0x).  There is no
              valid default.  If this option is not specified, the network
              number is obtained from the peer.  If the peer does not have the
              network number, the IPX protocol will not be started.

       ipx-node n:m
              Set the IPX node numbers. The two node numbers are separated
              from each other with a colon character. The first number n is
              the local node number. The second number m is the peer's node
              number. Each node number is a hexadecimal number, at most 10
              digits long. The node numbers on the ipx-network must be unique.
              There is no valid default. If this option is not specified then
              the node numbers are obtained from the peer.

       ipx-router-name <string>
              Set the name of the router. This is a string and is sent to the
              peer as information data.

       ipx-routing n
              Set the routing protocol to be received by this option. More
              than one instance of ipx-routing may be specified. The 'none'
              option (0) may be specified as the only instance of ipx-routing.
              The values may be 0 for NONE, 2 for RIP/SAP, and 4 for NLSP.

       ipxcp-accept-local
              Accept the peer's NAK for the node number specified in the
              ipx-node option. If a node number was specified, and non-zero,
              the default is to insist that the value be used. If you include
              this option then you will permit the peer to override the entry
              of the node number.

       ipxcp-accept-network
              Accept the peer's NAK for the network number specified in the
              ipx-network option. If a network number was specified, and non-
              zero, the default is to insist that the value be used. If you
              include this option then you will permit the peer to override
              the entry of the node number.

       ipxcp-accept-remote
              Use the peer's network number specified in the configure request
              frame. If a node number was specified for the peer and this
              option was not specified, the peer will be forced to use the
              value which you have specified.

       ipxcp-max-configure n
              Set the maximum number of IPXCP configure request frames which
              the system will send to n. The default is 10.

       ipxcp-max-failure n
              Set the maximum number of IPXCP NAK frames which the local
              system will send before it rejects the options. The default
              value is 3.

       ipxcp-max-terminate n
              Set the maximum number of IPXCP terminate request frames before
              the local system considers that the peer is not listening to
              them. The default value is 3.

       kdebug n
              Enable debugging code in the kernel-level PPP driver.  The
              argument values depend on the specific kernel driver, but in
              general a value of 1 will enable general kernel debug messages.
              (Note that these messages are usually only useful for debugging
              the kernel driver itself.)  For the Linux 2.2.x kernel driver,
              the value is a sum of bits: 1 to enable general debug messages,
              2 to request that the contents of received packets be printed,
              and 4 to request that the contents of transmitted packets be
              printed.  On most systems, messages printed by the kernel are
              logged by syslogd(8) to a file as directed in the
              /etc/syslog.conf configuration file.

       ktune  Enables pppd to alter kernel settings as appropriate.  Under
              Linux, pppd will enable IP forwarding (i.e. set
              /proc/sys/net/ipv4/ip_forward to 1) if the proxyarp option is
              used, and will enable the dynamic IP address option (i.e. set
              /proc/sys/net/ipv4/ip_dynaddr to 1) in demand mode if the local
              address changes.

       lcp-echo-failure n
              If this option is given, pppd will presume the peer to be dead
              if n LCP echo-requests are sent without receiving a valid LCP
              echo-reply.  If this happens, pppd will terminate the
              connection.  Use of this option requires a non-zero value for
              the lcp-echo-interval parameter.  This option can be used to
              enable pppd to terminate after the physical connection has been
              broken (e.g., the modem has hung up) in situations where no
              hardware modem control lines are available.

       lcp-echo-interval n
              If this option is given, pppd will send an LCP echo-request
              frame to the peer every n seconds.  Normally the peer should
              respond to the echo-request by sending an echo-reply.  This
              option can be used with the lcp-echo-failure option to detect
              that the peer is no longer connected.

       lcp-max-configure n
              Set the maximum number of LCP configure-request transmissions to
              n (default 10).

       lcp-max-failure n
              Set the maximum number of LCP configure-NAKs returned before
              starting to send configure-Rejects instead to n (default 10).

       lcp-max-terminate n
              Set the maximum number of LCP terminate-request transmissions to
              n (default 3).

       lcp-restart n
              Set the LCP restart interval (retransmission timeout) to n
              seconds (default 3).

       linkname name
              Sets the logical name of the link to name.  Pppd will create a
              file named ppp-name.pid in /var/run (or /etc/ppp on some
              systems) containing its process ID.  This can be useful in
              determining which instance of pppd is responsible for the link
              to a given peer system.  This is a privileged option.

       local  Don't use the modem control lines.  With this option, pppd will
              ignore the state of the CD (Carrier Detect) signal from the
              modem and will not change the state of the DTR (Data Terminal
              Ready) signal.  This is the opposite of the modem option.

       logfd n
              Send log messages to file descriptor n.  Pppd will send log
              messages to at most one file or file descriptor (as well as
              sending the log messages to syslog), so this option and the
              logfile option are mutually exclusive.  The default is for pppd
              to send log messages to stdout (file descriptor 1), unless the
              serial port is already open on stdout.

       logfile filename
              Append log messages to the file filename (as well as sending the
              log messages to syslog).  The file is opened with the privileges
              of the user who invoked pppd, in append mode.

       login  Use the system password database for authenticating the peer
              using PAP, and record the user in the system wtmp file.  Note
              that the peer must have an entry in the /etc/ppp/pap-secrets
              file as well as the system password database to be allowed
              access.

       maxconnect n
              Terminate the connection when it has been available for network
              traffic for n seconds (i.e. n seconds after the first network
              control protocol comes up).

       maxfail n
              Terminate after n consecutive failed connection attempts.  A
              value of 0 means no limit.  The default value is 10.

       modem  Use the modem control lines.  This option is the default.  With
              this option, pppd will wait for the CD (Carrier Detect) signal
              from the modem to be asserted when opening the serial device
              (unless a connect script is specified), and it will drop the DTR
              (Data Terminal Ready) signal briefly when the connection is
              terminated and before executing the connect script.  On Ultrix,
              this option implies hardware flow control, as for the crtscts
              option.  This is the opposite of the local option.

       mp     Enables the use of PPP multilink; this is an alias for the
              `multilink' option.  This option is currently only available
              under Linux.

       mppe-stateful
              Allow MPPE to use stateful mode.  Stateless mode is still
              attempted first.  The default is to disallow stateful mode.

       mpshortseq
              Enables the use of short (12-bit) sequence numbers in multilink
              headers, as opposed to 24-bit sequence numbers.  This option is
              only available under Linux, and only has any effect if multilink
              is enabled (see the multilink option).

       mrru n Sets the Maximum Reconstructed Receive Unit to n.  The MRRU is
              the maximum size for a received packet on a multilink bundle,
              and is analogous to the MRU for the individual links.  This
              option is currently only available under Linux, and only has any
              effect if multilink is enabled (see the multilink option).

       ms-dns <addr>
              If pppd is acting as a server for Microsoft Windows clients,
              this option allows pppd to supply one or two DNS (Domain Name
              Server) addresses to the clients.  The first instance of this
              option specifies the primary DNS address; the second instance
              (if given) specifies the secondary DNS address.  (This option
              was present in some older versions of pppd under the name
              dns-addr.)

       ms-wins <addr>
              If pppd is acting as a server for Microsoft Windows or "Samba"
              clients, this option allows pppd to supply one or two WINS
              (Windows Internet Name Services) server addresses to the
              clients.  The first instance of this option specifies the
              primary WINS address; the second instance (if given) specifies
              the secondary WINS address.

       multilink
              Enables the use of the PPP multilink protocol.  If the peer also
              supports multilink, then this link can become part of a bundle
              between the local system and the peer.  If there is an existing
              bundle to the peer, pppd will join this link to that bundle,
              otherwise pppd will create a new bundle.  See the MULTILINK
              section below.  This option is currently only available under
              Linux.

       name name
              Set the name of the local system for authentication purposes to
              name.  This is a privileged option.  With this option, pppd will
              use lines in the secrets files which have name as the second
              field when looking for a secret to use in authenticating the
              peer.  In addition, unless overridden with the user option, name
              will be used as the name to send to the peer when authenticating
              the local system to the peer.  (Note that pppd does not append
              the domain name to name.)

       noaccomp
              Disable Address/Control compression in both directions (send and
              receive).

       noauth Do not require the peer to authenticate itself.  This option is
              privileged.

       nobsdcomp
              Disables BSD-Compress compression; pppd will not request or
              agree to compress packets using the BSD-Compress scheme.

       noccp  Disable CCP (Compression Control Protocol) negotiation.  This
              option should only be required if the peer is buggy and gets
              confused by requests from pppd for CCP negotiation.

       nocrtscts
              Disable hardware flow control (i.e. RTS/CTS) on the serial port.
              If neither the crtscts nor the nocrtscts nor the cdtrcts nor the
              nocdtrcts option is given, the hardware flow control setting for
              the serial port is left unchanged.

       nocdtrcts
              This option is a synonym for nocrtscts. Either of these options
              will disable both forms of hardware flow control.

       nodefaultroute
              Disable the defaultroute option.  The system administrator who
              wishes to prevent users from creating default routes with pppd
              can do so by placing this option in the /etc/ppp/options file.

       nodeflate
              Disables Deflate compression; pppd will not request or agree to
              compress packets using the Deflate scheme.

       nodetach
              Don't detach from the controlling terminal.  Without this
              option, if a serial device other than the terminal on the
              standard input is specified, pppd will fork to become a
              background process.

       noendpoint
              Disables pppd from sending an endpoint discriminator to the peer
              or accepting one from the peer (see the MULTILINK section
              below).  This option should only be required if the peer is
              buggy.

       noip   Disable IPCP negotiation and IP communication.  This option
              should only be required if the peer is buggy and gets confused
              by requests from pppd for IPCP negotiation.

       noipv6 An alias for -ipv6.

       noipdefault
              Disables the default behavior when no local IP address is
              specified, which is to determine (if possible) the local IP
              address from the hostname.  With this option, the peer will have
              to supply the local IP address during IPCP negotiation (unless
              it specified explicitly on the command line or in an options
              file).

       noipx  Disable the IPXCP and IPX protocols.  This option should only be
              required if the peer is buggy and gets confused by requests from
              pppd for IPXCP negotiation.

       noktune
              Opposite of the ktune option; disables pppd from changing system
              settings.

       nolock Opposite of the lock option; specifies that pppd should not
              create a UUCP-style lock file for the serial device.  This
              option is privileged.

       nolog  Do not send log messages to a file or file descriptor.  This
              option cancels the logfd and logfile options.

       nomagic
              Disable magic number negotiation.  With this option, pppd cannot
              detect a looped-back line.  This option should only be needed if
              the peer is buggy.

       nomp   Disables the use of PPP multilink.  This option is currently
              only available under Linux.

       nomppe Disables MPPE (Microsoft Point to Point Encryption).  This is
              the default.

       nomppe-40
              Disable 40-bit encryption with MPPE.

       nomppe-128
              Disable 128-bit encryption with MPPE.

       nomppe-stateful
              Disable MPPE stateful mode.  This is the default.

       nompshortseq
              Disables the use of short (12-bit) sequence numbers in the PPP
              multilink protocol, forcing the use of 24-bit sequence numbers.
              This option is currently only available under Linux, and only
              has any effect if multilink is enabled.

       nomultilink
              Disables the use of PPP multilink.  This option is currently
              only available under Linux.

       nopcomp
              Disable protocol field compression negotiation in both the
              receive and the transmit direction.

       nopersist
              Exit once a connection has been made and terminated.  This is
              the default unless the persist or demand option has been
              specified.

       nopredictor1
              Do not accept or agree to Predictor-1 compression.

       noproxyarp
              Disable the proxyarp option.  The system administrator who
              wishes to prevent users from creating proxy ARP entries with
              pppd can do so by placing this option in the /etc/ppp/options
              file.

       notty  Normally, pppd requires a terminal device.  With this option,
              pppd will allocate itself a pseudo-tty master/slave pair and use
              the slave as its terminal device.  Pppd will create a child
              process to act as a `character shunt' to transfer characters
              between the pseudo-tty master and its standard input and output.
              Thus pppd will transmit characters on its standard output and
              receive characters on its standard input even if they are not
              terminal devices.  This option increases the latency and CPU
              overhead of transferring data over the ppp interface as all of
              the characters sent and received must flow through the character
              shunt process.  An explicit device name may not be given if this
              option is used.

       novj   Disable Van Jacobson style TCP/IP header compression in both the
              transmit and the receive direction.

       novjccomp
              Disable the connection-ID compression option in Van Jacobson
              style TCP/IP header compression.  With this option, pppd will
              not omit the connection-ID byte from Van Jacobson compressed
              TCP/IP headers, nor ask the peer to do so.

       papcrypt
              Indicates that all secrets in the /etc/ppp/pap-secrets file
              which are used for checking the identity of the peer are
              encrypted, and thus pppd should not accept a password which,
              before encryption, is identical to the secret from the
              /etc/ppp/pap-secrets file.

       pap-max-authreq n
              Set the maximum number of PAP authenticate-request transmissions
              to n (default 10).

       pap-restart n
              Set the PAP restart interval (retransmission timeout) to n
              seconds (default 3).

       pap-timeout n
              Set the maximum time that pppd will wait for the peer to
              authenticate itself with PAP to n seconds (0 means no limit).

       pass-filter-in filter-expression

       pass-filter-out filter-expression
              Specifies an incoming and outgoing packet filter to applied to
              data packets being sent or received to determine which packets
              should be allowed to pass.  Packets which are rejected by the
              filter are silently discarded.  This option can be used to
              prevent specific network daemons (such as routed) using up link
              bandwidth, or to provide a basic firewall capability.  The
              filter-expression syntax is as described for tcpdump(8), except
              that qualifiers which are inappropriate for a PPP link, such as
              ether and arp, are not permitted.  Generally the filter
              expression should be enclosed in single-quotes to prevent
              whitespace in the expression from being interpreted by the
              shell.  This option is currently only available under NetBSD,
              and then only if both the kernel and pppd were compiled with
              PPP_FILTER defined.

       password password-string
              Specifies the password to use for authenticating to the peer.
              Use of this option is discouraged, as the password is likely to
              be visible to other users on the system (for example, by using
              ps(1)).

       persist
              Do not exit after a connection is terminated; instead try to
              reopen the connection. The maxfail option still has an effect on
              persistent connections.

       plugin filename
              Load the shared library object file filename as a plugin.  This
              is a privileged option.  If filename does not contain a slash
              (/), pppd will look in the /usr/lib/pppd/version directory for
              the plugin, where version is the version number of pppd (for
              example, 2.4.2).

       predictor1
              Request that the peer compress frames that it sends using
              Predictor-1 compression, and agree to compress transmitted
              frames with Predictor-1 if requested.  This option has no effect
              unless the kernel driver supports Predictor-1 compression.

       privgroup group-name
              Allows members of group group-name to use privileged options.
              This is a privileged option.  Use of this option requires care
              as there is no guarantee that members of group-name cannot use
              pppd to become root themselves.  Consider it equivalent to
              putting the members of group-name in the kmem or disk group.

       proxyarp
              Add an entry to this system's ARP [Address Resolution Protocol]
              table with the IP address of the peer and the Ethernet address
              of this system.  This will have the effect of making the peer
              appear to other systems to be on the local ethernet.

       pty script
              Specifies that the command script is to be used to communicate
              rather than a specific terminal device.  Pppd will allocate
              itself a pseudo-tty master/slave pair and use the slave as its
              terminal device.  The script will be run in a child process with
              the pseudo-tty master as its standard input and output.  An
              explicit device name may not be given if this option is used.
              (Note: if the record option is used in conjunction with the pty
              option, the child process will have pipes on its standard input
              and output.)

       receive-all
              With this option, pppd will accept all control characters from
              the peer, including those marked in the receive asyncmap.
              Without this option, pppd will discard those characters as
              specified in RFC1662.  This option should only be needed if the
              peer is buggy.

       record filename
              Specifies that pppd should record all characters sent and
              received to a file named filename.  This file is opened in
              append mode, using the user's user-ID and permissions.  This
              option is implemented using a pseudo-tty and a process to
              transfer characters between the pseudo-tty and the real serial
              device, so it will increase the latency and CPU overhead of
              transferring data over the ppp interface.  The characters are
              stored in a tagged format with timestamps, which can be
              displayed in readable form using the pppdump(8) program.

       remotename name
              Set the assumed name of the remote system for authentication
              purposes to name.

       remotenumber number
              Set the assumed telephone number of the remote system for
              authentication purposes to number.

       refuse-chap
              With this option, pppd will not agree to authenticate itself to
              the peer using CHAP.

       refuse-mschap
              With this option, pppd will not agree to authenticate itself to
              the peer using MS-CHAP.

       refuse-mschap-v2
              With this option, pppd will not agree to authenticate itself to
              the peer using MS-CHAPv2.

       refuse-eap
              With this option, pppd will not agree to authenticate itself to
              the peer using EAP.

       refuse-pap
              With this option, pppd will not agree to authenticate itself to
              the peer using PAP.

       require-chap
              Require the peer to authenticate itself using CHAP [Challenge
              Handshake Authentication Protocol] authentication.

       require-mppe
              Require the use of MPPE (Microsoft Point to Point Encryption).
              This option disables all other compression types.  This option
              enables both 40-bit and 128-bit encryption.  In order for MPPE
              to successfully come up, you must have authenticated with either
              MS-CHAP or MS-CHAPv2.  This option is presently only supported
              under Linux, and only if your kernel has been configured to
              include MPPE support.

       require-mppe-40
              Require the use of MPPE, with 40-bit encryption.

       require-mppe-128
              Require the use of MPPE, with 128-bit encryption.

       require-mschap
              Require the peer to authenticate itself using MS-CHAP [Microsoft
              Challenge Handshake Authentication Protocol] authentication.

       require-mschap-v2
              Require the peer to authenticate itself using MS-CHAPv2
              [Microsoft Challenge Handshake Authentication Protocol, Version
              2] authentication.

       require-eap
              Require the peer to authenticate itself using EAP [Extensible
              Authentication Protocol] authentication.

       require-pap
              Require the peer to authenticate itself using PAP [Password
              Authentication Protocol] authentication.

       show-password
              When logging the contents of PAP packets, this option causes
              pppd to show the password string in the log message.

       silent With this option, pppd will not transmit LCP packets to initiate
              a connection until a valid LCP packet is received from the peer
              (as for the `passive' option with ancient versions of pppd).

       srp-interval n
              If this parameter is given and pppd uses EAP SRP-SHA1 to
              authenticate the peer (i.e., is the server), then pppd will use
              the optional lightweight SRP rechallenge mechanism at intervals
              of n seconds.  This option is faster than eap-interval
              reauthentication because it uses a hash-based mechanism and does
              not derive a new session key.

       srp-pn-secret string
              Set the long-term pseudonym-generating secret for the server.
              This value is optional and if set, needs to be known at the
              server (authenticator) side only, and should be different for
              each server (or poll of identical servers).  It is used along
              with the current date to generate a key to encrypt and decrypt
              the client's identity contained in the pseudonym.

       srp-use-pseudonym
              When operating as an EAP SRP-SHA1 client, attempt to use the
              pseudonym stored in ~/.ppp_psuedonym first as the identity, and
              save in this file any pseudonym offered by the peer during
              authentication.

       sync   Use synchronous HDLC serial encoding instead of asynchronous.
              The device used by pppd with this option must have sync support.
              Currently supports Microgate SyncLink adapters under Linux and
              FreeBSD 2.2.8 and later.

       unit num
              Sets the ppp unit number (for a ppp0 or ppp1 etc interface name)
              for outbound connections.

       updetach
              With this option, pppd will detach from its controlling terminal
              once it has successfully established the ppp connection (to the
              point where the first network control protocol, usually the IP
              control protocol, has come up).

       usehostname
              Enforce the use of the hostname (with domain name appended, if
              given) as the name of the local system for authentication
              purposes (overrides the name option).  This option is not
              normally needed since the name option is privileged.

       usepeerdns
              Ask the peer for up to 2 DNS server addresses.  The addresses
              supplied by the peer (if any) are passed to the /etc/ppp/ip-up
              script in the environment variables DNS1 and DNS2, and the
              environment variable USEPEERDNS will be set to 1.  In addition,
              pppd will create an /etc/ppp/resolv.conf file containing one or
              two nameserver lines with the address(es) supplied by the peer.

       user name
              Sets the name used for authenticating the local system to the
              peer to name.

       vj-max-slots n
              Sets the number of connection slots to be used by the Van
              Jacobson TCP/IP header compression and decompression code to n,
              which must be between 2 and 16 (inclusive).

       welcome script
              Run the executable or shell command specified by script before
              initiating PPP negotiation, after the connect script (if any)
              has completed.  A value for this option from a privileged source
              cannot be overridden by a non-privileged user.

       xonxoff
              Use software flow control (i.e. XON/XOFF) to control the flow of
              data on the serial port.

OPTIONS FILES
       Options can be taken from files as well as the command line.  Pppd
       reads options from the files /etc/ppp/options, ~/.ppprc and
       /etc/ppp/options.ttyname (in that order) before processing the options
       on the command line.  (In fact, the command-line options are scanned to
       find the terminal name before the options.ttyname file is read.)  In
       forming the name of the options.ttyname file, the initial /dev/ is
       removed from the terminal name, and any remaining / characters are
       replaced with dots.

       An options file is parsed into a series of words, delimited by
       whitespace.  Whitespace can be included in a word by enclosing the word
       in double-quotes (").  A backslash (\) quotes the following character.
       A hash (#) starts a comment, which continues until the end of the line.
       There is no restriction on using the file or call options within an
       options file.

SECURITY
       pppd provides system administrators with sufficient access control that
       PPP access to a server machine can be provided to legitimate users
       without fear of compromising the security of the server or the network
       it's on.  This control is provided through restrictions on which IP
       addresses the peer may use, based on its authenticated identity (if
       any), and through restrictions on which options a non-privileged user
       may use.  Several of pppd's options are privileged, in particular those
       which permit potentially insecure configurations; these options are
       only accepted in files which are under the control of the system
       administrator, or if pppd is being run by root.

       The default behaviour of pppd is to allow an unauthenticated peer to
       use a given IP address only if the system does not already have a route
       to that IP address.  For example, a system with a permanent connection
       to the wider internet will normally have a default route, and thus all
       peers will have to authenticate themselves in order to set up a
       connection.  On such a system, the auth option is the default.  On the
       other hand, a system where the PPP link is the only connection to the
       internet will not normally have a default route, so the peer will be
       able to use almost any IP address without authenticating itself.

       As indicated above, some security-sensitive options are privileged,
       which means that they may not be used by an ordinary non-privileged
       user running a setuid-root pppd, either on the command line, in the
       user's ~/.ppprc file, or in an options file read using the file option.
       Privileged options may be used in /etc/ppp/options file or in an
       options file read using the call option.  If pppd is being run by the
       root user, privileged options can be used without restriction.

       When opening the device, pppd uses either the invoking user's user ID
       or the root UID (that is, 0), depending on whether the device name was
       specified by the user or the system administrator.  If the device name
       comes from a privileged source, that is, /etc/ppp/options or an options
       file read using the call option, pppd uses full root privileges when
       opening the device.  Thus, by creating an appropriate file under
       /etc/ppp/peers, the system administrator can allow users to establish a
       ppp connection via a device which they would not normally have
       permission to access.  Otherwise pppd uses the invoking user's real UID
       when opening the device.

AUTHENTICATION
       Authentication is the process whereby one peer convinces the other of
       its identity.  This involves the first peer sending its name to the
       other, together with some kind of secret information which could only
       come from the genuine authorized user of that name.  In such an
       exchange, we will call the first peer the "client" and the other the
       "server".  The client has a name by which it identifies itself to the
       server, and the server also has a name by which it identifies itself to
       the client.  Generally the genuine client shares some secret (or
       password) with the server, and authenticates itself by proving that it
       knows that secret.  Very often, the names used for authentication
       correspond to the internet hostnames of the peers, but this is not
       essential.

       At present, pppd supports three authentication protocols: the Password
       Authentication Protocol (PAP), Challenge Handshake Authentication
       Protocol (CHAP), and Extensible Authentication Protocol (EAP).  PAP
       involves the client sending its name and a cleartext password to the
       server to authenticate itself.  In contrast, the server initiates the
       CHAP authentication exchange by sending a challenge to the client (the
       challenge packet includes the server's name).  The client must respond
       with a response which includes its name plus a hash value derived from
       the shared secret and the challenge, in order to prove that it knows
       the secret.  EAP supports CHAP-style authentication, and also includes
       the SRP-SHA1 mechanism, which is resistant to dictionary-based attacks
       and does not require a cleartext password on the server side.

       The PPP protocol, being symmetrical, allows both peers to require the
       other to authenticate itself.  In that case, two separate and
       independent authentication exchanges will occur.  The two exchanges
       could use different authentication protocols, and in principle,
       different names could be used in the two exchanges.

       The default behaviour of pppd is to agree to authenticate if requested,
       and to not require authentication from the peer.  However, pppd will
       not agree to authenticate itself with a particular protocol if it has
       no secrets which could be used to do so.

       Pppd stores secrets for use in authentication in secrets files
       (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP, MS-CHAP,
       MS-CHAPv2, and EAP MD5-Challenge, and /etc/ppp/srp-secrets for EAP
       SRP-SHA1).  All secrets files have the same format.  The secrets files
       can contain secrets for pppd to use in authenticating itself to other
       systems, as well as secrets for pppd to use when authenticating other
       systems to itself.

       Each line in a secrets file contains one secret.  A given secret is
       specific to a particular combination of client and server - it can only
       be used by that client to authenticate itself to that server.  Thus
       each line in a secrets file has at least 3 fields: the name of the
       client, the name of the server, and the secret.  These fields may be
       followed by a list of the IP addresses that the specified client may
       use when connecting to the specified server.

       A secrets file is parsed into words as for a options file, so the
       client name, server name and secrets fields must each be one word, with
       any embedded spaces or other special characters quoted or escaped.
       Note that case is significant in the client and server names and in the
       secret.

       If the secret starts with an `@', what follows is assumed to be the
       name of a file from which to read the secret.  A "*" as the client or
       server name matches any name.  When selecting a secret, pppd takes the
       best match, i.e.  the match with the fewest wildcards.

       Any following words on the same line are taken to be a list of
       acceptable IP addresses for that client.  If there are only 3 words on
       the line, or if the first word is "-", then all IP addresses are
       disallowed.  To allow any address, use "*".  A word starting with "!"
       indicates that the specified address is not acceptable.  An address may
       be followed by "/" and a number n, to indicate a whole subnet, i.e. all
       addresses which have the same value in the most significant n bits.  In
       this form, the address may be followed by a plus sign ("+") to indicate
       that one address from the subnet is authorized, based on the ppp
       network interface unit number in use.  In this case, the host part of
       the address will be set to the unit number plus one.

       Thus a secrets file contains both secrets for use in authenticating
       other hosts, plus secrets which we use for authenticating ourselves to
       others.  When pppd is authenticating the peer (checking the peer's
       identity), it chooses a secret with the peer's name in the first field
       and the name of the local system in the second field.  The name of the
       local system defaults to the hostname, with the domain name appended if
       the domain option is used.  This default can be overridden with the
       name option, except when the usehostname option is used.  (For EAP
       SRP-SHA1, see the srp-entry(8) utility for generating proper validator
       entries to be used in the "secret" field.)

       When pppd is choosing a secret to use in authenticating itself to the
       peer, it first determines what name it is going to use to identify
       itself to the peer.  This name can be specified by the user with the
       user option.  If this option is not used, the name defaults to the name
       of the local system, determined as described in the previous paragraph.
       Then pppd looks for a secret with this name in the first field and the
       peer's name in the second field.  Pppd will know the name of the peer
       if CHAP or EAP authentication is being used, because the peer will have
       sent it in the challenge packet.  However, if PAP is being used, pppd
       will have to determine the peer's name from the options specified by
       the user.  The user can specify the peer's name directly with the
       remotename option.  Otherwise, if the remote IP address was specified
       by a name (rather than in numeric form), that name will be used as the
       peer's name.  Failing that, pppd will use the null string as the peer's
       name.

       When authenticating the peer with PAP, the supplied password is first
       compared with the secret from the secrets file.  If the password
       doesn't match the secret, the password is encrypted using crypt() and
       checked against the secret again.  Thus secrets for authenticating the
       peer can be stored in encrypted form if desired.  If the papcrypt
       option is given, the first (unencrypted) comparison is omitted, for
       better security.

       Furthermore, if the login option was specified, the username and
       password are also checked against the system password database.  Thus,
       the system administrator can set up the pap-secrets file to allow PPP
       access only to certain users, and to restrict the set of IP addresses
       that each user can use.  Typically, when using the login option, the
       secret in /etc/ppp/pap-secrets would be "", which will match any
       password supplied by the peer.  This avoids the need to have the same
       secret in two places.

       Authentication must be satisfactorily completed before IPCP (or any
       other Network Control Protocol) can be started.  If the peer is
       required to authenticate itself, and fails to do so, pppd will
       terminated the link (by closing LCP).  If IPCP negotiates an
       unacceptable IP address for the remote host, IPCP will be closed.  IP
       packets can only be sent or received when IPCP is open.

       In some cases it is desirable to allow some hosts which can't
       authenticate themselves to connect and use one of a restricted set of
       IP addresses, even when the local host generally requires
       authentication.  If the peer refuses to authenticate itself when
       requested, pppd takes that as equivalent to authenticating with PAP
       using the empty string for the username and password.  Thus, by adding
       a line to the pap-secrets file which specifies the empty string for the
       client and password, it is possible to allow restricted access to hosts
       which refuse to authenticate themselves.

ROUTING
       When IPCP negotiation is completed successfully, pppd will inform the
       kernel of the local and remote IP addresses for the ppp interface.
       This is sufficient to create a host route to the remote end of the
       link, which will enable the peers to exchange IP packets.
       Communication with other machines generally requires further
       modification to routing tables and/or ARP (Address Resolution Protocol)
       tables.  In most cases the defaultroute and/or proxyarp options are
       sufficient for this, but in some cases further intervention is
       required.  The /etc/ppp/ip-up script can be used for this.

       Sometimes it is desirable to add a default route through the remote
       host, as in the case of a machine whose only connection to the Internet
       is through the ppp interface.  The defaultroute option causes pppd to
       create such a default route when IPCP comes up, and delete it when the
       link is terminated.

       In some cases it is desirable to use proxy ARP, for example on a server
       machine connected to a LAN, in order to allow other hosts to
       communicate with the remote host.  The proxyarp option causes pppd to
       look for a network interface on the same subnet as the remote host (an
       interface supporting broadcast and ARP, which is up and not a point-to-
       point or loopback interface).  If found, pppd creates a permanent,
       published ARP entry with the IP address of the remote host and the
       hardware address of the network interface found.

       When the demand option is used, the interface IP addresses have already
       been set at the point when IPCP comes up.  If pppd has not been able to
       negotiate the same addresses that it used to configure the interface
       (for example when the peer is an ISP that uses dynamic IP address
       assignment), pppd has to change the interface IP addresses to the
       negotiated addresses.  This may disrupt existing connections, and the
       use of demand dialing with peers that do dynamic IP address assignment
       is not recommended.

MULTILINK
       Multilink PPP provides the capability to combine two or more PPP links
       between a pair of machines into a single `bundle', which appears as a
       single virtual PPP link which has the combined bandwidth of the
       individual links.  Currently, multilink PPP is only supported under
       Linux.

       Pppd detects that the link it is controlling is connected to the same
       peer as another link using the peer's endpoint discriminator and the
       authenticated identity of the peer (if it authenticates itself).  The
       endpoint discriminator is a block of data which is hopefully unique for
       each peer.  Several types of data can be used, including locally-
       assigned strings of bytes, IP addresses, MAC addresses, randomly
       strings of bytes, or E-164 phone numbers.  The endpoint discriminator
       sent to the peer by pppd can be set using the endpoint option.

       In some circumstances the peer may send no endpoint discriminator or a
       non-unique value.  The bundle option adds an extra string which is
       added to the peer's endpoint discriminator and authenticated identity
       when matching up links to be joined together in a bundle.  The bundle
       option can also be used to allow the establishment of multiple bundles
       between the local system and the peer.  Pppd uses a TDB database in
       /var/run/pppd2.tdb to match up links.

       Assuming that multilink is enabled and the peer is willing to negotiate
       multilink, then when pppd is invoked to bring up the first link to the
       peer, it will detect that no other link is connected to the peer and
       create a new bundle, that is, another ppp network interface unit.  When
       another pppd is invoked to bring up another link to the peer, it will
       detect the existing bundle and join its link to it.

       If the first link terminates (for example, because of a hangup or a
       received LCP terminate-request) the bundle is not destroyed unless
       there are no other links remaining in the bundle.  Rather than exiting,
       the first pppd keeps running after its link terminates, until all the
       links in the bundle have terminated.  If the first pppd receives a
       SIGTERM or SIGINT signal, it will destroy the bundle and send a SIGHUP
       to the pppd processes for each of the links in the bundle.  If the
       first pppd receives a SIGHUP signal, it will terminate its link but not
       the bundle.

       Note: demand mode is not currently supported with multilink.

EXAMPLES
       The following examples assume that the /etc/ppp/options file contains
       the auth option (as in the default /etc/ppp/options file in the ppp
       distribution).

       Probably the most common use of pppd is to dial out to an ISP.  This
       can be done with a command such as

              pppd call isp

       where the /etc/ppp/peers/isp file is set up by the system administrator
       to contain something like this:

              ttyS0 19200 crtscts
              connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
              noauth

       In this example, we are using chat to dial the ISP's modem and go
       through any log on sequence required.  The /etc/ppp/chat-isp file
       contains the script used by chat; it could for example contain
       something like this:

              ABORT "NO CARRIER"
              ABORT "NO DIALTONE"
              ABORT "ERROR"
              ABORT "NO ANSWER"
              ABORT "BUSY"
              ABORT "Username/Password Incorrect"
              "" "at"
              OK "at&d0&c1"
              OK "atdt2468135"
              "name:" "^Umyuserid"
              "word:" "\qmypassword"
              "ispts" "\q^Uppp"
              "~-^Uppp-~"

       See the chat(8) man page for details of chat scripts.

       Pppd can also be used to provide a dial-in ppp service for users.  If
       the users already have login accounts, the simplest way to set up the
       ppp service is to let the users log in to their accounts and run pppd
       (installed setuid-root) with a command such as

              pppd proxyarp

       To allow a user to use the PPP facilities, you need to allocate an IP
       address for that user's machine and create an entry in
       /etc/ppp/pap-secrets, /etc/ppp/chap-secrets, or /etc/ppp/srp-secrets
       (depending on which authentication method the PPP implementation on the
       user's machine supports), so that the user's machine can authenticate
       itself.  For example, if Joe has a machine called "joespc" that is to
       be allowed to dial in to the machine called "server" and use the IP
       address joespc.my.net, you would add an entry like this to
       /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:

              joespc    server    "joe's secret" joespc.my.net

       (See srp-entry(8) for a means to generate the server's entry when
       SRP-SHA1 is in use.)  Alternatively, you can create a username called
       (for example) "ppp", whose login shell is pppd and whose home directory
       is /etc/ppp.  Options to be used when pppd is run this way can be put
       in /etc/ppp/.ppprc.

       If your serial connection is any more complicated than a piece of wire,
       you may need to arrange for some control characters to be escaped.  In
       particular, it is often useful to escape XON (^Q) and XOFF (^S), using
       asyncmap a0000.  If the path includes a telnet, you probably should
       escape ^] as well (asyncmap 200a0000).  If the path includes an rlogin,
       you will need to use the escape ff option on the end which is running
       the rlogin client, since many rlogin implementations are not
       transparent; they will remove the sequence [0xff, 0xff, 0x73, 0x73,
       followed by any 8 bytes] from the stream.

DIAGNOSTICS
       Messages are sent to the syslog daemon using facility LOG_DAEMON.
       (This can be overridden by recompiling pppd with the macro LOG_PPP
       defined as the desired facility.)  See the syslog(8) documentation for
       details of where the syslog daemon will write the messages.  On most
       systems, the syslog daemon uses the /etc/syslog.conf file to specify
       the destination(s) for syslog messages.  You may need to edit that file
       to suit.

       The debug option causes the contents of all control packets sent or
       received to be logged, that is, all LCP, PAP, CHAP, EAP, or IPCP
       packets.  This can be useful if the PPP negotiation does not succeed or
       if authentication fails.  If debugging is enabled at compile time, the
       debug option also causes other debugging messages to be logged.

       Debugging can also be enabled or disabled by sending a SIGUSR1 signal
       to the pppd process.  This signal acts as a toggle.

EXIT STATUS
       The exit status of pppd is set to indicate whether any error was
       detected, or the reason for the link being terminated.  The values used
       are:

       0      Pppd has detached, or otherwise the connection was successfully
              established and terminated at the peer's request.

       1      An immediately fatal error of some kind occurred, such as an
              essential system call failing, or running out of virtual memory.

       2      An error was detected in processing the options given, such as
              two mutually exclusive options being used.

       3      Pppd is not setuid-root and the invoking user is not root.

       4      The kernel does not support PPP, for example, the PPP kernel
              driver is not included or cannot be loaded.

       5      Pppd terminated because it was sent a SIGINT, SIGTERM or SIGHUP
              signal.

       6      The serial port could not be locked.

       7      The serial port could not be opened.

       8      The connect script failed (returned a non-zero exit status).

       9      The command specified as the argument to the pty option could
              not be run.

       10     The PPP negotiation failed, that is, it didn't reach the point
              where at least one network protocol (e.g. IP) was running.

       11     The peer system failed (or refused) to authenticate itself.

       12     The link was established successfully and terminated because it
              was idle.

       13     The link was established successfully and terminated because the
              connect time limit was reached.

       14     Callback was negotiated and an incoming call should arrive
              shortly.

       15     The link was terminated because the peer is not responding to
              echo requests.

       16     The link was terminated by the modem hanging up.

       17     The PPP negotiation failed because serial loopback was detected.

       18     The init script failed (returned a non-zero exit status).

       19     We failed to authenticate ourselves to the peer.

SCRIPTS
       Pppd invokes scripts at various stages in its processing which can be
       used to perform site-specific ancillary processing.  These scripts are
       usually shell scripts, but could be executable code files instead.
       Pppd does not wait for the scripts to finish (except for the ip-pre-up
       script).  The scripts are executed as root (with the real and effective
       user-id set to 0), so that they can do things such as update routing
       tables or run privileged daemons.  Be careful that the contents of
       these scripts do not compromise your system's security.  Pppd runs the
       scripts with standard input, output and error redirected to /dev/null,
       and with an environment that is empty except for some environment
       variables that give information about the link.  The environment
       variables that pppd sets are:

       DEVICE The name of the serial tty device being used.

       IFNAME The name of the network interface being used.

       IPLOCAL
              The IP address for the local end of the link.  This is only set
              when IPCP has come up.

       IPREMOTE
              The IP address for the remote end of the link.  This is only set
              when IPCP has come up.

       PEERNAME
              The authenticated name of the peer.  This is only set if the
              peer authenticates itself.

       SPEED  The baud rate of the tty device.

       ORIG_UID
              The real user-id of the user who invoked pppd.

       PPPLOGNAME
              The username of the real user-id that invoked pppd. This is
              always set.

       For the ip-down and auth-down scripts, pppd also sets the following
       variables giving statistics for the connection:

       CONNECT_TIME
              The number of seconds from when the PPP negotiation started
              until the connection was terminated.

       BYTES_SENT
              The number of bytes sent (at the level of the serial port)
              during the connection.

       BYTES_RCVD
              The number of bytes received (at the level of the serial port)
              during the connection.

       LINKNAME
              The logical name of the link, set with the linkname option.

       DNS1   If the peer supplies DNS server addresses, this variable is set
              to the first DNS server address supplied.

       DNS2   If the peer supplies DNS server addresses, this variable is set
              to the second DNS server address supplied.

       Pppd invokes the following scripts, if they exist.  It is not an error
       if they don't exist.

       /etc/ppp/auth-up
              A program or script which is executed after the remote system
              successfully authenticates itself.  It is executed with the
              parameters

              interface-name peer-name user-name tty-device speed

              Note that this script is not executed if the peer doesn't
              authenticate itself, for example when the noauth option is used.

       /etc/ppp/auth-down
              A program or script which is executed when the link goes down,
              if /etc/ppp/auth-up was previously executed.  It is executed in
              the same manner with the same parameters as /etc/ppp/auth-up.

       /etc/ppp/ip-pre-up
              A program or script which is executed just before the ppp
              network interface is brought up.  It is executed with the same
              parameters as the ip-up script (below).  At this point the
              interface exists and has IP addresses assigned but is still
              down.  This can be used to add firewall rules before any IP
              traffic can pass through the interface.  Pppd will wait for this
              script to finish before bringing the interface up, so this
              script should run quickly.

       /etc/ppp/ip-up
              A program or script which is executed when the link is available
              for sending and receiving IP packets (that is, IPCP has come
              up).  It is executed with the parameters

              interface-name tty-device speed local-IP-address
              remote-IP-address ipparam

       /etc/ppp/ip-down
              A program or script which is executed when the link is no longer
              available for sending and receiving IP packets.  This script can
              be used for undoing the effects of the /etc/ppp/ip-up and
              /etc/ppp/ip-pre-up scripts.  It is invoked in the same manner
              and with the same parameters as the ip-up script.

       /etc/ppp/ipv6-up
              Like /etc/ppp/ip-up, except that it is executed when the link is
              available for sending and receiving IPv6 packets. It is executed
              with the parameters

              interface-name tty-device speed local-link-local-address
              remote-link-local-address ipparam

       /etc/ppp/ipv6-down
              Similar to /etc/ppp/ip-down, but it is executed when IPv6
              packets can no longer be transmitted on the link. It is executed
              with the same parameters as the ipv6-up script.

       /etc/ppp/ipx-up
              A program or script which is executed when the link is available
              for sending and receiving IPX packets (that is, IPXCP has come
              up).  It is executed with the parameters

              interface-name tty-device speed network-number
              local-IPX-node-address remote-IPX-node-address
              local-IPX-routing-protocol remote-IPX-routing-protocol
              local-IPX-router-name remote-IPX-router-name ipparam pppd-pid

              The local-IPX-routing-protocol and remote-IPX-routing-protocol
              field may be one of the following:

              NONE      to indicate that there is no routing protocol
              RIP       to indicate that RIP/SAP should be used
              NLSP      to indicate that Novell NLSP should be used
              RIP NLSP  to indicate that both RIP/SAP and NLSP should be used

       /etc/ppp/ipx-down
              A program or script which is executed when the link is no longer
              available for sending and receiving IPX packets.  This script
              can be used for undoing the effects of the /etc/ppp/ipx-up
              script.  It is invoked in the same manner and with the same
              parameters as the ipx-up script.

FILES
       /var/run/pppn.pid (BSD or Linux), /etc/ppp/pppn.pid (others)
              Process-ID for pppd process on ppp interface unit n.

       /var/run/ppp-name.pid (BSD or Linux),
              /etc/ppp/ppp-name.pid (others) Process-ID for pppd process for
              logical link name (see the linkname option).

       /var/run/pppd2.tdb
              Database containing information about pppd processes, interfaces
              and links, used for matching links to bundles in multilink
              operation.  May be examined by external programs to obtain
              information about running pppd instances, the interfaces and
              devices they are using, IP address assignments, etc.
              /etc/ppp/pap-secrets Usernames, passwords and IP addresses for
              PAP authentication.  This file should be owned by root and not
              readable or writable by any other user.  Pppd will log a warning
              if this is not the case.

       /etc/ppp/chap-secrets
              Names, secrets and IP addresses for CHAP/MS-CHAP/MS-CHAPv2
              authentication.  As for /etc/ppp/pap-secrets, this file should
              be owned by root and not readable or writable by any other user.
              Pppd will log a warning if this is not the case.

       /etc/ppp/srp-secrets
              Names, secrets, and IP addresses for EAP authentication.  As for
              /etc/ppp/pap-secrets, this file should be owned by root and not
              readable or writable by any other user.  Pppd will log a warning
              if this is not the case.

       ~/.ppp_pseudonym
              Saved client-side SRP-SHA1 pseudonym.  See the srp-use-pseudonym
              option for details.

       /etc/ppp/options
              System default options for pppd, read before user default
              options or command-line options.

       ~/.ppprc
              User default options, read before /etc/ppp/options.ttyname.

       /etc/ppp/options.ttyname
              System default options for the serial port being used, read
              after ~/.ppprc.  In forming the ttyname part of this filename,
              an initial /dev/ is stripped from the port name (if present),
              and any slashes in the remaining part are converted to dots.

       /etc/ppp/peers
              A directory containing options files which may contain
              privileged options, even if pppd was invoked by a user other
              than root.  The system administrator can create options files in
              this directory to permit non-privileged users to dial out
              without requiring the peer to authenticate, but only to certain
              trusted peers.

SEE ALSO
       chat(8), pppstats(8)

       RFC1144
              Jacobson, V.  Compressing TCP/IP headers for low-speed serial
              links. February 1990.

       RFC1321
              Rivest, R.  The MD5 Message-Digest Algorithm. April 1992.

       RFC1332
              McGregor, G.  PPP Internet Protocol Control Protocol (IPCP). May
              1992.

       RFC1334
              Lloyd, B.; Simpson, W.A.  PPP authentication protocols. October
              1992.

       RFC1661
              Simpson, W.A.  The Point-to-Point Protocol (PPP). July 1994.

       RFC1662
              Simpson, W.A.  PPP in HDLC-like Framing. July 1994.

       RFC2284
              Blunk, L.; Vollbrecht, J., PPP Extensible Authentication
              Protocol (EAP). March 1998.

       RFC2472
              Haskin, D.  IP Version 6 over PPP December 1998.

       RFC2945
              Wu, T., The SRP Authentication and Key Exchange System September
              2000.

       draft-ietf-pppext-eap-srp-03.txt
              Carlson, J.; et al., EAP SRP-SHA1 Authentication Protocol. July
              2001.

NOTES
       Some limited degree of control can be exercised over a running pppd
       process by sending it a signal from the list below.

       SIGINT, SIGTERM
              These signals cause pppd to terminate the link (by closing LCP),
              restore the serial device settings, and exit.  If a connector or
              disconnector process is currently running, pppd will send the
              same signal to its process group, so as to terminate the
              connector or disconnector process.

       SIGHUP This signal causes pppd to terminate the link, restore the
              serial device settings, and close the serial device.  If the
              persist or demand option has been specified, pppd will try to
              reopen the serial device and start another connection (after the
              holdoff period).  Otherwise pppd will exit.  If this signal is
              received during the holdoff period, it causes pppd to end the
              holdoff period immediately.  If a connector or disconnector
              process is running, pppd will send the same signal to its
              process group.

       SIGUSR1
              This signal toggles the state of the debug option.

       SIGUSR2
              This signal causes pppd to renegotiate compression.  This can be
              useful to re-enable compression after it has been disabled as a
              result of a fatal decompression error.  (Fatal decompression
              errors generally indicate a bug in one or other implementation.)

AUTHORS
       Paul Mackerras (paulusATsamba.org), based on earlier work by Drew
       Perkins, Brad Clements, Karl Fox, Greg Christy, and Brad Parker.

COPYRIGHT
       Pppd is copyrighted and made available under conditions which provide
       that it may be copied and used in source or binary forms provided that
       the conditions listed below are met.  Portions of pppd are covered by
       the following copyright notices:

       Copyright (c) 1984-2000 Carnegie Mellon University. All rights
       reserved.
       Copyright (c) 1993-2004 Paul Mackerras. All rights reserved.
       Copyright (c) 1995 Pedro Roque Marques.  All rights reserved.
       Copyright (c) 1995 Eric Rosenquist.  All rights reserved.
       Copyright (c) 1999 Tommi Komulainen.  All rights reserved.
       Copyright (C) Andrew Tridgell 1999
       Copyright (c) 2000 by Sun Microsystems, Inc.  All rights reserved.
       Copyright (c) 2001 by Sun Microsystems, Inc.  All rights reserved.
       Copyright (c) 2002 Google, Inc.  All rights reserved.

       The copyright notices contain the following statements.

       Redistribution and use in source and binary forms, with or without
       modification, are permitted provided that the following conditions are
       met:

       1. Redistributions of source code must retain the above copyright
          notice, this list of conditions and the following disclaimer.

       2. Redistributions in binary form must reproduce the above copyright
          notice, this list of conditions and the following disclaimer in
          the documentation and/or other materials provided with the
          distribution.

       3. The name "Carnegie Mellon University" must not be used to
          endorse or promote products derived from this software without
          prior written permission. For permission or any legal
          details, please contact
            Office of Technology Transfer
            Carnegie Mellon University
            5000 Forbes Avenue
            Pittsburgh, PA  15213-3890
            (412) 268-4387, fax: (412) 268-7395
            tech-transferATandrew.edu

       3b. The name(s) of the authors of this software must not be used to
          endorse or promote products derived from this software without
          prior written permission.

       4. Redistributions of any form whatsoever must retain the following
          acknowledgments:
          "This product includes software developed by Computing Services
           at Carnegie Mellon University (http://www.cmu.edu/computing/)."
          "This product includes software developed by Paul Mackerras
           <paulusATsamba.org>".
          "This product includes software developed by Pedro Roque Marques
           <pedro_mATyahoo.com>".
          "This product includes software developed by Tommi Komulainen
           <Tommi.KomulainenATiki.fi>".

       CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
       SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
       FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE FOR ANY
       SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
       RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
       CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
       CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

       THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
       THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
       FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY SPECIAL,
       INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
       FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
       NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
       WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.



                                                                       PPPD(8)