PPPOE-SNIFF(8) System Manager's Manual PPPOE-SNIFF(8)
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 success-
fully connect rather than try to pry them out of the DSL provider.
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 firstname.lastname@example.org along with the name of your ISP
and the manufacturer and model number of your DSL modem. This informa-
tion 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
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 <dfsATroaringpenguin.com>.
The pppoe home page is http://www.roaringpenguin.com/pppoe/.
pppd(8), pppoe(8), pppoe-sniff(8), pppoe-relay(8),
4th Berkeley Distribution 3 July 2000 PPPOE-SNIFF(8)