This Tech Note explains how you can do this, and gives a sample scenario. With dynamic NAT, translations don't exist in the NAT translation table until the router receives traffic that requires translation.
Dynamic translations have a timeout period after which they are purged from the translation table.
This entry translates the inside global address back to the inside local address, which means that devices on the outside cloud can send packets to the global address 172.16.131.1 and reach the device on the inside cloud, which has the local address 10.10.10.1. No other translations are generated or entered into the translation table until the router receives a packet on its inside interface with a source address permitted by access-list 7. When the router receives a packet destined for one of these global addresses, it checks the translation table for an existing translation. If there is none, it tries to route the packet, which in this case means back out the serial interface. Using the ip nat outside source static Command .