Defining Static Address Translations

Static address translation establishes a one-to-one mapping between a local and global address or local and global address/port pair. When you specify a static address translation or address/port pair translation, you issue commands to indicate how the translation is applied, along with more specific variables that further define the type of translation.

Caution: You must mark interfaces that participate in NAT translation as on the inside or the outside network. See Specifying Inside and Outside Interfaces for details.

Creating Static Inside Source Translations

You use the ip nat inside source static command to create static translations from a local IP address to a global IP address, and to untranslate the destination address when a packet returns from the outside network to the inside network. When you configure traditional NAT (both basic NAT and NAPT), you only need to use this command alone. However, when you configure twice NAT, you must also use ip nat outside source static .

The ip nat inside source static command creates a simple (IP address only) or extended (IP address, port, and protocol) entry in the translation table that maps the two addresses.

ip nat inside source static

Creating Static Outside Source Translations

Less commonly used, outside source translation enables you to set up translation between two non-unique or not publicly routable networks (for example, two separate networks that use overlapping IP address blocks).

ip nat outside source static