PPTP

NAME

SYNOPSIS

DESCRIPTION

pptp 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 service providers.

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 pppd.  

OPTIONS

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.

--phone <number>

Pass <number> to remote host as phone number

--nolaunchpppd

Do not launch pppd but use stdin as the network connection. Use this flag when including pptp as a pppd connection process using the pty option. See EXAMPLES.

--quirks <quirk>

Work around a buggy PPTP implementation, adopts special case handling for particular PPTP servers and ADSL modems. Currently recognised values are BEZEQ_ISRAEL only

--debug

Run in foreground (for debugging with gdb)

--sync

Enable Synchronous HDLC (pppd must use it too)

--timeout <secs>

Time to wait for reordered packets (0.01 to 10 secs)

--nobuffer

Completely disables buffering and reordering of packets. Any --timeout specified will be ignored.

--idle-wait <secs>

Time to wait before sending a control connection echo request. The RFC2637 default is 60 seconds.

--max-echo-wait <secs>

Time to wait for an echo reply before closing the control connection. The RFC2637 default is 60 seconds.

--logstring <name>

Use <name> instead of 'anon' in syslog messages

--localbind <addr>

Bind to specified IP address instead of wildcard

--loglevel <level>

Sets the debugging level (0=low, 1=default, 2=high)

--test-type <n>

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.

--test-rate <n>

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.

QUIRKS

BEZEQ_ISRAEL

modifies packets to interoperate with Orckit ADSL modems on the BEZEQ network in Israel.

EXAMPLES

Connection to a Microsoft Windows VPN Server

pppdnoauthnobsdcompnodeflaterequire-mppe-128namedomain\\\\usernameremotenamePPTPptypptp 10.0.0.5 --nolaunchpppd

Note that the chap-secrets file used by pppd must include an entry for domain\\username

STATISTICS

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):

rx accepted

the number of GRE packets successfully passed to PPP

rx lost

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)

rx buffered

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

rx truncated

the number of times we received a packet which was shorter than the length implied by the GRE header

rx invalid

the number of times we received a packet which had invalid or unsupported flags set in the header, wrong version, or wrong protocol.

rx acks

the number of pure acknowledgements received (without data). Too many of these will waste bandwidth, and might be solved by tuning the remote host.

tx sent

the number of GRE packets sent with data

tx failed

the number of packets we tried to send, but the OS reported an error

tx short

the number of times the OS would not let us write a complete packet

tx acks

the number of times we sent a pure ack, without data

tx oversize

the number of times we couldn't send a packet because it was over PACKET_MAX bytes long

round trip

the estimated round-trip time in milliseconds

SEE ALSO

Documentation in /usr/share/doc/pptp  

AUTHOR