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Old 01-16-2010, 03:53 AM   #1
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Please help! Iptables

I am a big fan of Fedora 11. Also, I am using wireless broadband USB to access internet. For the sake of practising Iptables, I configured my Iptables as the following:

# Generated by iptables-save v1.4.3.1 on Sat Jan 16 16:50:19 2010
:INPUT DROP [49:5544]
:OUTPUT ACCEPT [50:2918]
-A INPUT -i lo -j ACCEPT
-A INPUT -d -p tcp -m tcp --tcp-flags FIN,SYN,ACK FIN,SYN,ACK -j AC
-A INPUT -d -p tcp -m state --state RELATED,ESTABLISHED -j
-A INPUT -d -p tcp -m state --state NEW -m tcp --sport 80 -
-A INPUT -d -p tcp -m state --state NEW -m tcp --sport 443
-A INPUT -d -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A INPUT -d -p icmp -m icmp --icmp-type 11 -j ACCEPT
-A INPUT -d -p icmp -m icmp --icmp-type 0 -j ACCEPT
# Completed on Sat Jan 16 16:50:19 2010

When I use "service iptables stop". I can access internet. But when I start iptables, I couldn't access internet. Then I use this command "netstat -ant" to check if there is anything blocking access to internet. And this is the result:

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0 :::111 :::* LISTEN
tcp 0 0 :::22 :::* LISTEN
tcp 0 0 ::1:631 :::* LISTEN

It seems like there is something wrong with my iptables configuration but I am at my wit's end. I couldn't figure out why I couldn't access internet with my iptables on. And I am also Linux newbie. Any help would be appreciated.
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Old 01-16-2010, 04:26 AM   #2
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Currently you allow "-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT" from your loopback device ( aka "lo") but not your wireless network device. Check the output of ifconfig and iwconfig to find the devices name. Also please search LQ of "iptables" as we've got quite some threads by now listing rulesets you could read and use after modification.
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