pppoe-sniff - examine network for non-standard PPPoE frames
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 Ether-
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 operat-
ing 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 email@example.com 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 promis-
ifconfig eth0 -promisc
The -I option specifies the Ethernet interface to use. Under Linux, it is typi-
cally 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 exit.
pppoe-sniff only works on Linux.
pppoe-sniff was written by David F. Skoll <firstname.lastname@example.org>.
The pppoe home page is http://www.roaringpenguin.com/pppoe/.
adsl-start(8), adsl-stop(8), adsl-connect(8), pppd(8), pppoe.conf(5), pppoe(8), adsl-set-
up(8), adsl-status(8), pppoe-server(8), pppoe-relay(8)
4th Berkeley Distribution 3 July 2000 PPPOE-SNIFF(8)