Auto NAT
All NAT rules that are configured as a parameter of a network object are considered to be auto NAT rules. This is a quick and easy way to configure NAT for a network object. You cannot create these rules for a group object, however.
Although these rules are configured as part of the object itself, you cannot see the NAT configuration in the object definition through the object manager.
When a packet enters an interface, both the source and destination IP addresses are checked against the auto NAT rules. The source and destination address in the packet can be translated by separate rules if separate matches are made. These rules are not tied to each other; different combinations of rules can be used depending on the traffic.
Because the rules are never paired, you cannot specify that sourceA/destinationA should have a different translation than sourceA/destinationB. Use manual NAT for that kind of functionality, where you can identify the source and destination address in a single rule.