ip nat inside source
Translates the source of IP packets that are traveling inside to outside.
Translates the destination of the IP packets that are traveling outside to inside.
ip nat outside source
Translates the source of the IP packets that are traveling outside to inside.
Translates the destination of the IP packets that are traveling inside to outside.
Reference:
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094e77.shtml
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_configuration_example09186a0080093f8e.shtml
