From my CCIE Lab preparation Note
outbound packets — change SOURCE —inside source <original ip><–>
outbound packets — change DESTIN —outside source <–><original ip>
inbound packets — change SOURCE —outside source <original ip><–>
inbound packets — change DESTIN —inside source <–><original ip>
*Packets that router generated will be NATed by single “ip nat outside” command in “destination NAT” form.
***If someone do not understand this, please analyze it by yourself. I almost forget everything about my notes. Maybe I will explain it later — may be 2 years later…….