Original: This mechanism is implemented in a routing device that uses stateful translation tables to map the '' hidden '' addresses into a single address and then rewrites the outgoing Internet Protocol ( IP ) packets on exit so that they appear to originate from the router .
Simplified: Such kind of firewalls use translation tables to map the '' hidden '' addresses into a single address and then rewrites the outgoing IP packets on exit from the router so that they appear to originate from the router .