Defining Dynamic Translation Rules

You can use the CLI to define dynamic translation rules for inside and outside sources.

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.

You can create a dynamic translation rule to configure inside source or outside source translation. If the NAT router cannot locate a matching entry in its translation database for a given packet, it evaluates the access list of all applicable dynamic translation rules (inside source translation rules for outbound packets and outside source translation rules for inbound packets) against the packet. If an access list permits translation, the NAT router tries to allocate an address from the associated address pool to install a new translation.

When you create dynamic translation rules, keep the following in mind:

• You can associate a list with one pool at any given time. Associating a list with a different pool replaces the previous association.
• The optional overload keyword for inside source translation specifies that the router employ NAPT.
• You can configure dynamic NAPT for inside source translation only; you cannot configure dynamic NAPT for outside source translation.
• When no match occurs for any dynamic translation rule, the NAT router does not translate the packet.
• When an address pool is empty, the NAT router drops the packet.
• Access lists and pools do not have to exist when you are defining dynamic translation rules; you may create them after you define the dynamic translations.

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