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



NAME
       pppd - Point to Point Protocol daemon

SYNOPSIS
       pppd [ tty_name ] [ speed ] [ options ]

DESCRIPTION
       The  Point-to-Point  Protocol  (PPP) provides a method for transmitting
       datagrams over serial point-to-point links.  PPP is composed  of  three
       parts:  a  method  for  encapsulating  datagrams  over serial links, an
       extensible Link Control Protocol (LCP), and a family of Network Control
       Protocols  (NCP)  for  establishing  and configuring different network-
       layer protocols.

       The encapsulation scheme is provided by  driver  code  in  the  kernel.
       Pppd  provides  the  basic  LCP, authentication support, and an NCP for
       establishing and configuring the Internet Protocol (IP) (called the  IP
       Control Protocol, IPCP).

FREQUENTLY USED OPTIONS
       tty_name
              Communicate  over  the  named  device.   The  string  "/dev/" is
              prepended if necessary.  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  Set the baud rate to speed (a decimal number).  On systems  such
              as 4.4BSD and NetBSD, any speed can be specified.  Other systems
              (e.g. SunOS) allow only a limited set of speeds.

       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 syn-
              tax 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.

       asyncmap map
              Set the async character map to map.  This  map  describes  which
              control  characters  cannot  be  successfully  received over the
              serial line.  Pppd will ask the peer to send these characters as
              a  2-byte  escape sequence.  The argument is a 32 bit hex number
              with each  bit  representing  a  character  to  escape.   Bit  0
              (00000001) represents the character 0x00; bit 31 (80000000) rep-
              resents the character 0x1f or ^_.  If multiple asyncmap  options
              are  given, the values are ORed together.  If no asyncmap option
              is given, no async character map  will  be  negotiated  for  the
              receive direction; the peer should then escape all control char-
              acters.   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  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
              Use  the  executable or shell command specified by script to set
              up the serial line.  This script would typically use the chat(8)
              program  to  dial the modem and start the remote ppp session.  A
              value for this option from a privileged source cannot  be  over-
              ridden by a non-privileged user.

       crtscts
              Use  hardware flow control (i.e. RTS/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  unidirec-
              tional  flow  control. The serial port will suspend transmission
              when requested by the modem (via CTS)  but  will  be  unable  to
              request  the  modem  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 spec-
              ified.

       disconnect script
              Run the executable or shell command specified  by  script  after
              pppd  has  terminated the link.  This script 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 transmis-
              sion (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 com-
              mas.  Note that almost any character can be  specified  for  the
              escape option, unlike the asyncmap option which only allows con-
              trol 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
              Run the executable or shell command specified by script to  ini-
              tialize  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 over-
              ridden 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.

       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  minimum  MRU
              value is 128.  The default MRU value is 1500.  A value of 296 is
              recommended for slow links (40 bytes for  TCP/IP  header  +  256
              bytes of data).  (Note that for IPv6 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
              IPv6 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  with-
              out 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  ran-
              domized.

       active-filter filter-expression
              Specifies  a  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  pack-
              ets)  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).

       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 corre-
              sponding 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  con-
              trol  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  chal-
              lenges) to n seconds (default 3).

       connect-delay n
              Wait for up 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  appro-
              priately (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 corre-
              sponding direction.  Use  nodeflate  or  deflate  0  to  disable
              Deflate compression entirely.  (Note: pppd requests Deflate com-
              pression 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 speci-
              fied  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 avail-
              able, 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  con-
              junction with the demand option.

       domain d
              Append  the domain name d to the local host name for authentica-
              tion 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  val-
              ues 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  sys-
              tem,  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.

       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 pack-
              ets) 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 speci-
              fied 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 sec-
              onds (default 3).

       ipparam string
              Provides an extra parameter to the ip-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  sys-
              tem  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 argu-
              ment 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 config-
              uration 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 connec-
              tion.  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 sec-
              onds (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 sys-
              tems) containing its process ID.  This can be useful  in  deter-
              mining  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.

       logfd n
              Send log messages to file descriptor n.  Pppd will send log mes-
              sages 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 ter-
              minated and before executing the  connect  script.   On  ULTRIX,
              this  option  implies  hardware flow control, as for the crtscts
              option.

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

       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 (Win-
              dows  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 sec-
              tion  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.)

       netmask n
              Set  the  interface  netmask  to n, a 32 bit netmask in "decimal
              dot" notation (e.g. 255.255.255.0).  If this  option  is  given,
              the  value  specified  is  ORed  with  the default netmask.  The
              default netmask is chosen based  on  the  negotiated  remote  IP
              address; it is the appropriate network mask for the class of the
              remote IP address, ORed with the netmasks for any non  point-to-
              point  network  interfaces  in  the system which are on the same
              network.   (Note:  on  some  platforms,  pppd  will  always  use
              255.255.255.255 for the netmask, if that is the only appropriate
              value for a point-to-point interface.)

       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 stan-
              dard 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 speci-
              fied,  which  is to determine (if possible) the local IP address
              from the hostname.  With this option, the peer will have to sup-
              ply  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.

       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.

       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 speci-
              fied.

       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 sec-
              onds (default 3).

       pap-timeout n
              Set the maximum time that pppd will wait for the peer to authen-
              ticate 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  pre-
              vent  specific  network  daemons  (such as routed) using up link
              bandwidth, or to provide a basic firewall capability.  The  fil-
              ter-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 expres-
              sion 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.

       persist
              Do not exit after a connection is  terminated;  instead  try  to
              reopen the connection.

       plugin filename
              Load  the shared library object file filename as a plugin.  This
              is a privileged option.

       predictor1
              Request that the peer compress frames that it sends  using  Pre-
              dictor-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.  With-
              out 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 trans-
              fer 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 dis-
              played in readable form using the pppdump(8) program.

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

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

       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-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).

       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.

       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 pur-
              poses (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.  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 Jacob-
              son 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 white-
       space.  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 admin-
       istrator, or if pppd is being run by root.

       The default behavior 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 connec-
       tion.  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 inter-
       net 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  permis-
       sion  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 pass-
       word) with the server, and authenticates  itself  by  proving  that  it
       knows  that secret.  Very often, the names used for authentication cor-
       respond to the internet hostnames of the peers, but this is not  essen-
       tial.

       At  present,  pppd  supports two authentication protocols: the Password
       Authentication Protocol (PAP) and the Challenge  Handshake  Authentica-
       tion  Protocol  (CHAP).  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.

       The  PPP  protocol, being symmetrical, allows both peers to require the
       other to authenticate itself.  In that case, two separate and  indepen-
       dent  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 behavior 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).  Both
       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  accept-
       able  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  disal-
       lowed.  To allow any address, use "*".  A word starting with "!"  indi-
       cates 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  net-
       work  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.

       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 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 remote-
       name 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 pass-
       word 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  pass-
       word  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  termi-
       nated 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 authenti-
       cate 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 pass-
       word, 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.   Communica-
       tion  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  communi-
       cate 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 nego-
       tiated  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 indi-
       vidual 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  circumstances the peer may send no endpoint discriminator or a non-
       unique value.  The optional 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/pppd.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.  Currently, if  the
       first  pppd  terminates (for example, because of a hangup or a received
       signal) the bundle is destroyed.

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 con-
       tains 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 "atd0c1"
              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 or /etc/ppp/chap-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"  which  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

       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 transpar-
       ent; 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.)  In order to see the error and debug
       messages, you will need to edit your /etc/syslog.conf  file  to  direct
       the messages to the desired output device or file.

       The  debug  option  causes  the contents of all control packets sent or
       received to be logged, that is, all LCP, PAP,  CHAP  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.  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) dur-
              ing 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.

       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-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  script.
              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 pack-
              ets 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).

       /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 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/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  privi-
              leged  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
       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.

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

NOTES
       The following signals have the specified effect when sent to pppd.

       SIGINT, SIGTERM
              These signals cause pppd to terminate the link (by closing LCP),
              restore the serial device settings, and exit.

       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.

       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 (Paul.MackerrasATcs.au), based on earlier work by
       Drew Perkins, Brad Clements, Karl Fox, Greg Christy, and Brad Parker.



                                                                       PPPD(8)