iptables -t nat -F
nic #
 iptables -F
nic #
 iptables -t nat -L
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination         
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
nic #
 # NAT
nic #
 iptables -t nat -A POSTROUTING -s 192.1.3.0/24 -p udp --sport 4500 -j SNAT --to-source 192.1.2.254:3500-3700
nic #
 iptables -t nat -A POSTROUTING -s 192.1.3.0/24 -p udp --sport 500 -j SNAT --to-source 192.1.2.254:2500-2700
nic #
 iptables -t nat -A POSTROUTING --source 192.1.3.0/24 --destination 0.0.0.0/0 -j SNAT --to-source 192.1.2.254
nic #
 echo done
done