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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?

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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

1 Answer

up vote 1 down vote

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.

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