Hi all

As per the below given snippet NVI is used when nat domains (inside and
outside) are not required. But a NVI is created either when you configure
"ip nat inside", "ip nat outside" or "ip nat enable" on interface for the
first time and it used that interface's IP address. It seems the NVI is just
getting un-numbered to the first interface with NAT.

My understanding is that NVI enables the IOS to add route to routing table
with "add-route" keyword which can be redistributed.  Is there any other key
functionality of NVI.


Snippet from
http://www.cisco.com/en/US/docs/ios/ipaddr/configuration/guide/iadnat_addr_consv_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1085114

The NAT Virtual Interface (NVI) feature removes the requirement to configure
an interface as either NAT inside or NAT outside. An interface can be
configured to use or not use NAT.

The NVI feature allows NAT traffic flows on the virtual interface,
eliminating the need to specify inside and outside domains. When a domain is
specified, the translation rules are applied either before or after the
route decisions depending on the traffic flow from inside to outside or
outside to inside. The translation rules are applied only after the route
decision for an NVI.
Benefits of a NAT Virtual Interface

•A NAT table is maintained per interface for better performance and
scalability.

•Domain-specific NAT configurations can be eliminated.



With regards
Kings
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