# Define contact IP addresses

Contact addresses are required when NAT is applied between to SMC components. You can define contact addresses for NGFW Engines, Master NGFW Engines, and most types of server elements.

The contact addresses are defined in the element properties. The contact addresses are based on Location elements. You can also define a Default contact address that is used whenever no contact address is defined for a certain Location.

You create the Locations and add elements to the Locations based on how your network is set up. Then you define the Contact Addresses for each element for each Location in the properties of the elements. All SMC components in other Locations then use the addresses defined for their Location for contact.