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default- information-originate keyword. However, an NSSA is
different from a stub, because when the router is an ASBR, it can import
a default external AS route (for routing protocol domains adjacent to the
NSSA but not within the OSPF AS) into the NSSA using the
default-information-originate keyword.
• External routes advertised into an NSSA can include network
destinations outside the AS learned via OSPF, the default route, static
routes, routes imported from other routing protocols such as RIP, and
networks directly connected to the router that are not running OSPF.
• NSSA external LSAs (Type 7) are converted by any ABR adjacent to the
NSSA into external LSAs (Type-5), and propagated into other areas
within the AS.
• Also, note that unlike stub areas, all Type-3 summary LSAs are always
imported into NSSAs to ensure that internal routes are always chosen
over Type-7 NSSA external routes.
• This router supports up to 16 total areas (either normal transit areas,
stubs, or NSSAs).
Example
This example creates a stub area 10.3.0.0, and assigns all interfaces with class
B addresses 10.3.x.x to the NSSA. It also instructs the router to generate
external LSAs into the NSSA when it is an NSSA ABR or NSSA ASBR.
Console(config-router)#area 10.3.0.0 nssa
default-information-originate
Console(config-router)#network 10.3.0.0 255.255.0.0 area 10.2.0.0
Console(config-router)#