setting up a firewall from scratch

["Mansour Al-Aqeel" <mansour77@ownmail.net>]

Hi Everybody:
I need an advice from someone about what to do. I have a small lan and
looking to connect it to the net through a LinkSys router using OpenWrt.
The router comes with a built in rules that does everything. However,
I'm a new to iptables, and therefore it would be good chance for me to
be introduced to this tool. I need to delete all the built in rules and
recteate them again from scratch in order to know what each of them
does... I wrote a small script to excute and save my rules in. The
router stopps responding when I excute the script, and I have to reboot
it. All I need at this point is to disable any connection attempt from
out side ($WAN) and enable everything on the ($LAN) side. Here's what I
did so far. Can any one tell me what's next, or what I'm missing ??


#delete all the existing rules from all chains
iptables -F INPUT
iptables -F OUTPUT
iptables -F FORWARD

#set the default policy on the external interface not to accept anything
iptables -P INPUT -i $WAN -j REJECT  # dont let anything coming from
outside
iptables -P OUTPUT -i $WAN -j ACCEPT # let anything go out
iptables -P FORWARD -i $WAN -j REJECT # dont forward anyhting from
outside to inside

#######################################
## allow everyThign internally
#######################################
iptables -f filter -A INPUT -i $LAN -j ACCEPT
iptables -f filter -A INPUT -o $LAN -j ACCEPT

iptable  -A OUTPUT -i $LAN -j ACCEPT
iptable -A OUTPUT -o $LAN -j ACCEPT

####forward internally through the br0
iptables -f filter -A FORWARD -i $LAN -j ACCEPT
iptables -f filter -A FORWARD -o $LAN -j ACCEPT


Thanx
-- 
  Mansour Al-Aqeel
  mansour77@ownmail.net

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