IP Tables slows network response times

Michael Hallager michael at networkstuff.co.nz
Sun Aug 14 11:33:57 CEST 2005

Hello all.

I have spent rather a lot of time trying to find an answer for this one.

I have a Slackware Linux box, 2.4.29 kernel running IP Tables. I have the bare 
number of needed modules compiled into the custom kernel.

I start IP Tables using the following batch file:

iptables -P INPUT DROP
iptables -A INPUT -p tcp --destination-port 22 -j ACCEPT
iptables -A INPUT -p tcp --destination-port 25 -j ACCEPT
iptables -A INPUT -p tcp --destination-port 53 -j ACCEPT
iptables -A INPUT -p udp --destination-port 53 -j ACCEPT
iptables -A INPUT -p tcp --destination-port 80 -j ACCEPT
iptables -A INPUT -p tcp --destination-port 110 -j ACCEPT
iptables -A INPUT -p tcp --destination-port 443 -j ACCEPT

This works except it makes webpages and email served from this box SLOW to 
respond. (Several seconds).

Any ideas please? Questions welcomed.

Michael Hallager
networkStuff ltd
www.networkstuff.co.nz | p.09.839.1000 | m.029.638.7883

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