Someone

# cat nat.sh
#!/bin/sh
EXTIP="`/sbin/ifconfig br0 | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`"
/sbin/depmod -a
/sbin/modprobe ip_tables
/sbin/modprobe ip_conntrack
/sbin/modprobe iptable_nat
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
iptables -F
iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP
iptables -t nat -F

#Accept external
iptables -A FORWARD -i br0 -o eth2 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i eth2 -o br0 -j ACCEPT

#QUEUE: 
#iptables -A FORWARD -j QUEUE

#FORWARD
iptables -t nat -A PREROUTING -p tcp --dport 443 -j DNAT --to 192.168.3.105:443
iptables -t nat -A PREROUTING -p tcp --dport 1741 -j DNAT --to 192.168.3.105:1741
iptables -t nat -A PREROUTING -p tcp --dport 1742 -j DNAT --to 192.168.3.105:1742

#NAT 
iptables -t nat -A POSTROUTING -s 192.168.3.105 -o $EXTIF -j SNAT --to 6X.X.X.X