xl2tpd.conf(5) File Formats Manual xl2tpd.conf(5)

xl2tpd.conf - L2TPD configuration file

The xl2tpd.conf file contains configuration information for xl2tpd, the free implementation of l2tp protocol.

The configuration file is composed of sections and parameters. Each section has a given name which will be used when using the configuration FIFO (normally /var/run/xl2tpd/l2tp-control). See xl2tpd.8 for more details.

The specific given name default will specify parameters applicable for all the following sections.

Specify where to find the authentication file used to authenticate l2tp tunnels. The default is /etc/xl2tpd/l2tp-secrets.

Use IPsec Security Association tracking. When this is enabled, packets received by xl2tpd should have two extra fields (refme and refhim) which allows tracking of multiple clients using the same internal NATed IP address, and allows tracking of multiple clients behind the same NAT router. This needs to be supported by the kernel. Currently, this only works with Openswan KLIPS in "mast" mode. (see http://www.openswan.org/)

Set this to yes and the system will provide proper SAref values in the recvmsg() calls.

Values can be 'yes' or 'no'. The default is 'no'.

When using IPsec Security Association trackinng, a new setsockopt is used. Since this is not (yet?) an official Linux kernel option, we got bumped. Openswan upto 2.6.35 for linux kernels up to 2.6.35 used a saref num of 22. Linux 3.6.36+ uses 22 for IP_NODEFRAG. We moved our IP_IPSEC_REFINFO to 30. If not set, the default is to use 30. For older SAref patched kernels, use 22.

The IP address of the interface on which the daemon listens. By default, it listens on INADDR_ANY (0.0.0.0), meaning it listens on all interfaces.

Specify which UDP port xl2tpd should use. The default is 1701.

If set to 'yes', the xl2tpd process will only accept connections from peers addresses specified in the following sections. The default is 'no'.

Set this to 'yes' to enable syslog output of L2TP AVP debugging information.

Set this to 'yes' to enable syslog output of network debugging information.

Set this to 'yes' to enable printing of L2TP packet debugging information. Note: Output goes to STDOUT, so use this only in conjunction with the -D command line option.

Set this to 'yes' to enable syslog output of FSM debugging information.

Set this to 'yes' to enable syslog output of tunnel debugging information.

Specify how many retries before a tunnel is closed. If there is no tunnel, then stop re-transmitting. The default is 5.

If set to 'yes', only one control tunnel will be allowed to be built between 2 peers.

(no) ip range
Specify the range of IP addresses the LNS will assign to the connecting LAC PPP tunnels. Multiple ranges can be defined. Using the 'no' statement disallows the use of that particular range. Ranges are defined using the format IP - IP (example: 1.1.1.1 - 1.1.1.10). Note that either at least one ip range option must be given, or you must set assign ip to no.

Set this to 'no' if xl2tpd should not assign IP addresses out of the pool defined with the ip range option. This can be useful if you have some other means to assign IP addresses, e. g. a pppd that supports RADIUS AAA.

(no) lac
Specify the IP addresses of LAC's which are allowed to connect to xl2tpd acting as a LNS. The format is the same as the ip range option.

If set to 'yes', xl2tpd will use the AVP hiding feature of L2TP. To get more information about hidden AVP's and AVP in general, refer to rfc2661 (add URL?)

Use the following IP as xl2tpd's own IP address.

Specify the range of addresses the LNS will assign as the local address to connecting LAC PPP tunnels. This option is mutually exclusive with the local ip option and is useful in cases where it is desirable to have a unique IP address for each tunnel. Specify the range value exactly like the ip range option. Note that the assign ip option has no effect on this option.

If set to 'yes', the length bit present in the l2tp packet payload will be used.

(refuse | require) chap
Will require or refuse the remote peer to get authenticated via CHAP for the ppp authentication.

(refuse | require) pap
Will require or refuse the remote peer to get authenticated via PAP for the ppp authentication.

(refuse | require) authentication
Will require or refuse the remote peer to authenticate itself.

If set to 'yes', /etc/passwd will be used for remote peer ppp authentication.

Will report this as the xl2tpd hostname in negotiation.

This will enable the debug for pppd.

Pass the peer's IP address to pppd as ipparam. Enabled by default.

Specify the path for a file which contains pppd configuration parameters to be used.

This option is deprecated and no longer functions. It used to be used to define the flow control window size for individual L2TP calls or sessions. The L2TP standard (RFC2661) no longer defines flow control or window sizes on calls or sessions.

This defines the window size of the control channel. The window size is defined as the number of outstanding unacknowledged packets, not as a number of bytes.

If set to 'yes', sequence numbers will be included in the communication. The feature to use sequence numbers in sessions is currently broken and does not function.

If set to 'yes', use challenge authentication to authenticate peer.

If set, the receive bandwidth maximum will be set to this value

If set, the transmit bandwidth maximum will be set to this value

The following are LAC specific configuration flags. Most of those described in the LNS section may be used in a LAC context, where it makes common sense (essentially l2tp protocols tuning flags and authentication / ppp related ones).

Set the dns name or ip address of the LNS to connect to.

If set to 'yes', xl2tpd will automatically dial the LAC during startup.

If set to 'yes', xl2tpd will attempt to redial if the call get disconnected. Note that, if enabled, xl2tpd will keep passwords in memory: a potential security risk.

redial timeout
Wait X seconds before redial. The redial option must be set to yes to use this option. Defaults to 30 seconds.

Will give up redial tries after X attempts.

/etc/xl2tpd/xl2tpd.conf
Configuration file of xl2tpd, used by default.

/etc/xl2tpd/l2tp-secrets
Secrets file, used by default.

/var/run/xl2tpd/l2tp-control
Control file, used by default.

Please use the github project page https://github.com/xelerance/xl2tpd to send bugreports, issues and any other feedback

xl2tpd(8), xl2tpd-control(8), pppd(8)

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program (see the file LICENSE); if not, see https://www.gnu.org/licenses/, or contact Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

Alexander Dorokhov <alex.dorokhov@gmail.com>
Alexander Naumov <alexander_naumov@opensuse.org>

Forked from l2tpd by Xelerance: https://github.com/xelerance/xl2tpd

Michael Richardson <mcr@xelerance.com>
Paul Wouters <paul@xelerance.com>
Samir Hussain <shussain@xelerance.com>

Previous development was hosted at sourceforge (http://www.sourceforge.net/projects/l2tpd) by:

Scott Balmos <sbalmos@iglou.com>
David Stipp <dstipp@one.net>
Jeff McAdams <jeffm@iglou.com>

Based off of l2tpd version 0.61. Many thanks to Jacco de Leeuw <jacco2@dds.nl> for maintaining l2tpd.
Copyright (C)1998 Adtran, Inc.
Mark Spencer <markster@marko.net>

Jan 2022