iptables DNAT 範例

echo "1" > /proc/sys/net/ipv4/ip_forward

IF=vmbr0
PORT_FROM=80
PORT_TO=80
DEST=192.168.1.1

iptables -t nat -A POSTROUTING -o ${IF} -j MASQUERADE
iptables -t nat -A PREROUTING -p tcp --dport PORT_FROM -j DNAT --to-destination ${DEST}:${PORT_TO}

or 

iptables -t nat -A PREROUTING -i $IF -p tcp --dport $PORT_FROM -j DNAT --to $DEST:$PORT_TO
iptables -t nat -A POSTROUTING -p tcp -d $DEST --dport $PORT_TO -j MASQUERADE

SNAT
iptables -t nat -A POSTROUTING -s 172.16.255.0/255.255.255.0 -o vmbr0 -j SNAT --to-source 192.168.1.1