> Yes, nice and easy does it, although the man pages can sometimes be
> cryptic to newbies like me.

i'm afraid the man pages are oftentimes the best reference you have.
but here's a packet filtering howto for iptables

http://www.netfilter.org/documentation/HOWTO//packet-filtering-HOWTO.html

here's a simple iptables script to get you started ( i hope the comments
i put in are clear enough ):



#!/bin/sh

# flush all rules
iptables -F

# accept all connections from the local interface, all protocols
iptables -A INPUT -i lo -p all -j ACCEPT
iptables -A OUTPUT -o lo -p all -j ACCEPT

# accept all established connections
# may background ka naman siguro on TCP/IP
iptables -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT

#all of this should be in one line
#some email clients automatically format text
#last words should be : --reject-with tcp-reset
iptables -A INPUT -p tcp --tcp-option ! 2 -j REJECT --reject-with tcp-reset

#open http port
iptables -A INPUT -s 192.168.1.0/24 -p tcp -i eth0 --dport 80 -j ACCEPT

#allow ssh connections 
iptables -A INPUT -s 192.168.1.0/24 -p tcp -i eth0 --dport 22 -j ACCEPT

# add other things you want here


#drop all other connections
iptables -P INPUT DROP



note that the rules here checks only the packets coming from the INPUT
chain  and does not care about the packets going out of your unit.



ramil

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