Dynamic Address Translations

Dynamic NAT is configured using a standard access-list, a NAT address pool, and a source list.

IPv4 NAT pool addresses are assigned as a range with a starting address and ending address. IPv6 NAT pools are assigned as a combination of a start address and prefix length and count, where count specifies a contiguous block of addresses from 1 to the value specified by count.

NAT pool IP addresses used in dynamic NATing are reassigned whenever they become free. Dynamic NAT bindings time out and are deleted due to idleness. A NAT translation timeout option is configurable for dynamic translations and defaults to 240 seconds.

The NAT source list is used to configure dynamic NAT. This is an association of an access-list and a NAT pool. The access list specifies the internal client source IP addresses that match the source list and the pool specifies the NAT pool to assign global IP addresses from. If a source list is configured as “overloaded” this means the NAT translations will use NAPT and the NAT pool may multiplex multiple private IP addresses to one NAT pool global address. NAPT translation is supported for IPv4 only.

You can also specify the egress VLAN interface for which this source list will be applied. Otherwise, the source list applies to all interfaces.