establishes the client side of a Virtual Private Network (VPN) using
the Point-to-Point Tunneling Protocol (PPTP). Use this program to
connect to an employer's PPTP based VPN, or to certain cable and ADSL
By default, pptp establishes the PPTP call to the PPTP server,
and then starts an instance of pppd to manage the data transfer.
However, pptp can also be run as a connection manager within
The first non-option argument on the pptp command line must be the host
name or IP address of the PPTP server.
All long options (starting with "--")
are interpreted as pptp options, and a fatal error occurs if an
unrecognised option is used.
All command-line arguments which do not start
with "-" are interpreted as ppp options, and passed as is to pppd unless
--nolaunchpppd is given.
Pass <number> to remote host as phone number
Do not launch
but use stdin as the network connection. Use this flag when including
connection process using the
option. See EXAMPLES.
Work around a buggy PPTP implementation, adopts special case handling for
particular PPTP servers and ADSL modems.
Currently recognised values are BEZEQ_ISRAEL only
Run in foreground (for debugging with gdb)
Enable Synchronous HDLC (pppd must use it too)
Time to wait for reordered packets (0.01 to 10 secs)
Completely disables buffering and reordering of packets.
Any --timeout specified will be ignored.
Time to wait before sending a control connection echo request.
The RFC2637 default is 60 seconds.
Time to wait for an echo reply before closing the control connection.
The RFC2637 default is 60 seconds.
Use <name> instead of 'anon' in syslog messages
Bind to specified IP address instead of wildcard
Sets the debugging level (0=low, 1=default, 2=high)
Enable packet reordering tests that damage the integrity of the packet
stream to the server. Use this only when testing servers. Zero is
the default, and means that packets are sent in the correct order. A
value of one (1) causes a single swap between two packets, such that
the sequence numbers might be 1 2 3 4 6 5 7 8 9. A value of two (2)
causes ten packets to be buffered, then sent out of order but
ascending, such that the sequence numbers might be 1 2 3 4 16 6 7 8 9
10 11 12 13 14 15 17 18 19 20. A value of three (3) causes ten
packets to be buffered, then sent in the reverse order, like this; 1 2
3 4 16 15 14 13 12 11 10 9 8 7 6 5 17 18 19 20.
Sets the number of packets to pass before causing a reordering test.
Default is 100. Has no effect if test-type is zero. The result of
test types 2 and 3 are undefined if this value is less than ten.
modifies packets to interoperate with Orckit ADSL modems on the BEZEQ
network in Israel.
Note that the chap-secrets file used by pppd must include an entry for domain\\username
The pptp process collects statistics when sending and receiving
GRE packets. They are intended to be useful for debugging poor PPTP
performance and for general monitoring of link quality. The statistics
are cumulative since the pptp process was started.
The statistics can be viewed by sending a SIGUSR1 signal to the
"GRE-to-PPP Gateway" process, which will cause it to dump them
to the system logs (at the LOG_NOTICE level). A better way to present
the statistics to applications is being sought (e.g. SNMP?).
The following statistics are collected at the time of writing (April 2003):
the number of GRE packets successfully passed to PPP
the number of packets never received, and presumed lost in the network
rx under win
the number of packets which were duplicates or had old sequence numbers
(this might be caused by a packet-reordering network if your reordering
timeout is set too low)
rx over win
the number of packets which were too far ahead in the sequence to be
reordered (might be caused by loss of more than 300 packets in a row)
the number of packets which were slightly ahead of sequence, and were
either buffered for reordering, or if buffering is disabled, accepted
immediately (resulting in the intermediate packets being discarded).
rx OS errors
the number of times where the operating system reported an error when
we tried to read a packet
the number of times we received a packet which was shorter than the
length implied by the GRE header
the number of times we received a packet which had invalid or unsupported
flags set in the header, wrong version, or wrong protocol.
the number of pure acknowledgements received (without data). Too many
of these will waste bandwidth, and might be solved by tuning the remote host.
the number of GRE packets sent with data
the number of packets we tried to send, but the OS reported an error
the number of times the OS would not let us write a complete packet
the number of times we sent a pure ack, without data
the number of times we couldn't send a packet because it was over
PACKET_MAX bytes long