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       pppoe-sniff - examine network for non-standard PPPoE frames


       pppoe-sniff [options]


       pppoe-sniff  listens  for  likely-looking PPPoE PADR and session frames
       and deduces extra options required for pppoe(8) to work.

       Some DSL providers seem to  use  non-standard  frame  types  for  PPPoE
       frames,  and/or  require a certain value in the Service-Name field.  It
       is often easier  to  sniff  those  values  from  a  machine  which  can
       successfully  connect  rather  than  try  to  pry  them  out of the DSL

       To use pppoe-sniff, you need two computers, a DSL modem and an Ethernet
       hub (not an Ethernet switch.)

       If the DSL modem normally connects directly to your computer’s Ethernet
       card, connect it to the "uplink" port on the Ethernet  hub.   Plug  two
       computers  into normal ports on the hub.  On one computer, run whatever
       software the DSL provider gave you on whatever operating system the DSL
       provider  supports.   On  the  other  computer, run Linux and log in as

       On the Linux machine, put the Ethernet interface into promiscuous  mode
       and start pppoe-sniff.  If the ethernet interface is eth0, for example,
       type these commands:

            ifconfig eth0 promisc
            pppoe-sniff -I eth0

       On the other machine, start your DSL  connection  as  usual.   After  a
       short  time,  pppoe-sniff should print recommendations for the value of
       PPPOE_EXTRA.  Set this value in  /etc/ppp/pppoe.conf.   If  pppoe-sniff
       indicates  that something special is required in PPPOE_EXTRA, please e-
       mail this to along with the name of  your  ISP
       and  the  manufacturer  and  model  number  of  your  DSL  modem.  This
       information will be collated and provided on the  PPPoE  web  page  for
       users who do not have two computers.

       After  pppoe-sniff finishes (or you stop it if it seems hung), remember
       to turn off promiscuous mode:

            ifconfig eth0 -promisc


       -I interface
              The -I option specifies the Ethernet interface  to  use.   Under
              Linux,  it  is  typically eth0 or eth1.  The interface should be
              "up" and in promiscuous mode before you start pppoe-sniff.

       -V     The -V option causes pppoe-sniff to print its version number and


       pppoe-sniff only works on Linux.


       pppoe-sniff was written by David F. Skoll <>.

       The pppoe home page is


       pppd(8),        pppoe(8),        pppoe-sniff(8),        pppoe-relay(8),