Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

When I create the only rule disabling all input,

iptables -P INPUT DROP

I can not connect anything. So it looks like I should allow some incoming activity to get PPPoE working correctly. What rules should I add?

share|improve this question
That rule alone doesn't break your connection, I have that in my config as well, but notice that pppoe-connect script changes iptables automatically (if you configured it to apply a "firewall") – warl0ck Oct 19 '12 at 14:57

A good first rule is

iptables -I INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

This will allow any traffic in that is on or related to an outgoing connection.

Technically, PPPoE will be working correctly as the PPPoE packets will not be filtered by the firewall as they are below the IP layer (iptables sets up rules for IPv4 packets). However the IP packets coming out of PPP will be filtered, which is why you need the above rule.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.