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PPPD(8)								       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.	This option is privileged if the noauth	option
	      is used.

       _speed_
	      Set the baud rate	to <speed> (a  decimal	number).   On  systems
	      such as 4.4BSD and NetBSD, any speed can be specified, providing
	      that it is supported by the serial device	driver.	 Other systems
	      (e.g. SunOS, Linux) allow	only a limited set of speeds.

       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-dialling mode.  This	option is useful  in  conjunc-
	      tion  with  the  idle  option if there are packets being sent or
	      received regularly over the link (for example, routing  informa-
	      tion  packets)  which would otherwise prevent the	link from ever
	      appearing	to  be	idle.	The  filter-expression	syntax	is  as
	      described	for tcpdump(1),	except that qualifiers which are inap-
	      propriate	for a PPP link,	such as	ether and arp, are not permit-
	      ted.  Generally the filter expression should be enclosed in sin-
	      gle-quotes to prevent whitespace in the  expression  from	 being
	      interpreted  by  the  shell.  This option	only available 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.

       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.
	      This option is privileged	if the noauth option is	used.

       connect-max-attempts _n_
	      Attempt dial-out connection to remote system no more than	speci-
	      fied number of times (default = 1).  If the  connection  is  not
	      made, pppd will exit.  Requires that persist has been specified.

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

       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.	This option is
	      privileged if the	noauth option is used.

       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.

       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).

       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.

       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	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.

       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.

       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).

       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 8 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 behaviour
	      is  not  desired,	 use  the  nopersist  option  after the	demand
	      option.  The idle	and holdoff options are	also useful in conjuc-
	      tion 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.

       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	option	is 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 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.

       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 spec-
	      ified 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	nuber 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 n is	a number which is the sum of the following  values:  1
	      to enable	general	debug messages,	2 to request that the contents
	      of received packets be printed, and 4 to request that  the  con-
	      tents  of	transmitted packets be printed.	 On most systems, mes-
	      sages printed by the kernel are logged by	syslog(1) to a file as
	      directed in the /etc/syslog.conf configuration file.

       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).

       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.

       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).

       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.

       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.

       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.

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

       noauth Do not require the peer to authenticate itself.  This option  is
	      privileged  if the auth option is	specified in /etc/ppp/options.

       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 option  is  given,  the
	      hardware	flow  control  setting	for  the  serial  port is left
	      unchanged.

       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.

       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.

       noipdefault
	      Disables the default behaviour when no local IP address is spec-
	      ified,  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.

       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.

       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 comprssion.

       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.

       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 filter-expression
	      Specifies	a 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(1),	except that qualifiers which are inap-
	      propriate	for a PPP link,	such as	ether and arp, are not permit-
	      ted.  Generally the filter expression should be enclosed in sin-
	      gle-quotes  to  prevent  whitespace in the expression from being
	      interpreted by the shell.	 Note that it  is  possible  to	 apply
	      different	constraints to incoming	and outgoing packets using the
	      inbound and outbound qualifiers.	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.

       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.

       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.

       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.

       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).

       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).

       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.	This option is privileged if the noauth	option
	      is used.

       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.	 In part this is provided by the /etc/ppp/options file,	 where
       the  administrator can place options to restrict	the ways in which pppd
       can be used, and	in part	by the PAP and CHAP secrets files,  where  the
       administrator  can  restrict  the  set of IP addresses which individual
       users may use.

       The normal way that pppd	should be set up is to have the	auth option in
       the  /etc/ppp/options  file.   (This  may  become  the default in later
       releases.)  If users wish to use	pppd to	dial out to a peer which  will
       refuse  to  authenticate	itself (such as	an internet service provider),
       the  system  administrator  should  create  an	options	  file	 under
       /etc/ppp/peers  containing  the	noauth	option,	the name of the	serial
       port to use, and	the connect  option  (if  required),  plus  any	 other
       appropriate  options.   In  this	 way, pppd can be set up to allow non-
       privileged users	to make	unauthenticated	connections  only  to  trusted
       peers.

       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.

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 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).	  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.  Any
       following  words	 on the	same line are taken to be a list of acceptable
       IP addresses  for  that	client,	 or  an	 override  for	"local:remote"
       addresses  (the	same format used on the	command	line or	in the options
       file) when on a line that contains a specific client name (not a	 wild-
       card  nor  empty).   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	speci-
       fied 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.  Note that case is  sig-
       nificant	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.

       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.

       Additional checks are performed when the	login option is	used.  If  the
       file  /etc/ppp/ppp.deny	exists,	 and  the  user	 is  listed in it, the
       authentication fails.  If the file /etc/ppp/ppp.shells exists  and  the
       user's normal login shell is not	listed,	the authentication fails.

       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 dialling with	peers that do dynamic IP address assignment is
       not recommended.

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  logon 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 "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 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 overriden 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.

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.

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

       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/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.

       /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.

       /etc/ppp/ppp.deny
	      Lists users who may not use the system password PAP  authentica-
	      tion.

       /etc/ppp/ppp.shells
	      Lists  user  shells  which  are approved for system password PAP
	      authentication logins.

       /usr/share/examples/pppd/
	      Sample pppd configuration	files.

SEE ALSO
       chat(8),	ppp(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.

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.Mackerras@cs.anu.edu.au), based on earlier work by
       Drew Perkins, Brad Clements, Karl Fox, Greg Christy, and	Brad Parker.

								       PPPD(8)

NAME | SYNOPSIS | DESCRIPTION | FREQUENTLY USED OPTIONS | OPTIONS | OPTIONS FILES | SECURITY | AUTHENTICATION | ROUTING | EXAMPLES | DIAGNOSTICS | SCRIPTS | FILES | SEE ALSO | NOTES | AUTHORS

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