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this is my sample script
FWVER=0.63
echo -e "\n\nLoading simple rc.firewall version
$FWVER..\n"
IPTABLES=/sbin/iptables EXTIF="eth1" INTIF1="eth0" INTIF2="ppp0" INTIF3="ppp1" echo " External Interface: $EXTIF"
echo " Internal Interface: $INTIF1" echo " Internal Interface: $INTIF2" echo " Internal Interface: $INTIF3" echo -en " loading modules: "
echo " - Verifying that all kernel modules are ok"
/sbin/depmod -a echo -en "ip_tables, "
/sbin/insmod ip_tables echo -en "ip_conntrack, " /sbin/insmod ip_conntrack echo -en "ip_conntrack_ftp, " /sbin/insmod ip_conntrack_ftp echo -en "ip_conntrack_irc, " /sbin/insmod ip_conntrack_irc echo -en "iptable_nat, " /sbin/insmod iptable_nat echo -en "ip_nat_ftp, " /sbin/insmod ip_nat_ftp echo ". Done loading modules."
echo " enabling forwarding.."
echo "1" > /proc/sys/net/ipv4/ip_forward echo " enabling DynamicAddr.." echo "1" > /proc/sys/net/ipv4/ip_dynaddr echo " clearing any existing rules and setting default policy.." $IPTABLES -P INPUT ACCEPT $IPTABLES -F INPUT $IPTABLES -P OUTPUT ACCEPT $IPTABLES -F OUTPUT $IPTABLES -P FORWARD DROP $IPTABLES -F FORWARD $IPTABLES -t nat -F echo " FWD: Allow all connections OUT and only existing and
related ones IN"
$IPTABLES -A FORWARD -i $EXTIF -o $INTIF1 -m state --state
ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF1 -o $EXTIF -j ACCEPT $IPTABLES -A FORWARD -i $EXTIF -o $INTIF2 -m state --state ESTABLISHED,RELATED -j ACCEPT $IPTABLES -A FORWARD -i $INTIF2 -o $EXTIF -j ACCEPT $IPTABLES -A FORWARD -i $EXTIF -o $INTIF3 -m state --state
ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF3 -o $EXTIF -j ACCEPT $IPTABLES -A FORWARD -j LOG
$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE echo -e "\nrc.firewall-2.4 v$FWVER done.\n"
[root@delllinux rc.d]# !ip iptables -L FORWARD Chain FORWARD (policy DROP) target prot opt source destination ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT all -- anywhere anywhere ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT all -- anywhere anywhere ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT all -- anywhere anywhere LOG all -- anywhere anywhere LOG level warning [root@delllinux rc.d]# iptables -t nat -A PREROUTING --dst 192.168.2.90 -p tcp --dport 4899 -j DNAT --to-destination 192.168.1.2 My problem is for the iptables command above to work I have to issue the
command "iptables -P FORWARD ACCEPT" Can anyone tell me how to allow just
certain forwarding so I can set the default to DENY? And is this firewall script
secure enough?
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