pppoe(8) - OpenBSD manual pages

SYNOPSIS

pppoe [-sv] [-i interface] [-n service] [-p system]

DESCRIPTION

The pppoe program can, with the help of ppp(8), act as a server or client for running PPP Over Ethernet.

The options are as follows:

-i interface: Specify the interface that pppoe is to use, which should be a real Ethernet interface (not a virtual device like tun(4)). If this option is not specified, pppoe will use the first Ethernet interface that is up and running.
-n service: Use service as the service name when negotiating with the server. By default, the client will ask for any service, and expect the server to respond with the same.
-p system: This argument is passed, uninterpreted, to ppp(8). It can be used to specify the configuration data to be used for PPP Over Ethernet connections. This option is only used in server mode.
-s: If this option is specified, pppoe will run as a server. Otherwise, pppoe runs as a client.
-v: For each use of the flag, the verbosity of pppoe increases.

Configuring the client involves setting up the configuration file for ppp(8). The following statements must be included in the file for the specified system (or ``default'' if no system is specified):

set device "!/usr/sbin/pppoe"
set mtu max 1492
set mru max 1492
set speed sync
disable acfcomp protocomp
deny acfcomp

The set device line tells ppp to use the pppoe program for input and output instead of using a serial port or other network connection. The mtu and mru must be set to 1492 to leave room in the outgoing Ethernet packet for the pppoe headers. The set speed sync line tells ppp to use synchronous encoding for the packets sent between it and pppoe. According to RFC 2516, protocol compression, protocomp, is not recommended, so it is disabled, but not denied. On the other hand, address and control field compression, acfcomp, must be disabled and denied.

Additionally, the authentication mechanism for the connection must be specified as well as any other parameters.

EXAMPLE CONFIGURATION

Given a machine with one Ethernet interface, xl0, the first thing that must be done is to bring the interface up:

# ifconfig xl0 up

This can be done automatically during boot with a /etc/hostname.xl0 file, see hostname.if(5) for details.

Next, a /etc/ppp/ppp.conf file must be created. Below is a minimal PPPoE style configuration, see ppp(8) for more options.

default:
   set log Phase Chat LCP IPCP CCP tun command

pppoe:
   set device "!/usr/sbin/pppoe -i xl0"
   set mtu max 1492
   set mru max 1492
   set speed sync
   disable acfcomp protocomp
   deny acfcomp
   set authname "myUsername"
   set authkey "myPassword"

The default section sets up some helpful information to log while getting started, and the pppoe section sets the required fields for a PPPoE connection as well as the username and password to use to authenticate to the service provider.

Once the /etc/ppp/ppp.conf file is set up, it is just a matter of setting ppp(8) into action:

# ppp pppoe
Working in interactive mode
Using interface: tun0
ppp ON deepthought> dial
Ppp ON deepthought>
PPp ON deepthought>
PPP ON deepthought>

The userland ppp(8) daemon has many options for configuration, like adding default routes, network address translation, automatically using remote DNS servers, automatic dialing, etc. Please see ppp(8) for details.

Several ppp(8) options are particularly helpful when used with pppoe.

enable lqr / accept lqr: Enable and accept link quality requests, which can be used to detect whether the link has gone down.
enable mssfixup: Allow ppp(8) to adjust the maximum segment size on outgoing SYN packets.

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