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default-information-originate
- When the router is an NSSA Area Border
Router (ABR) or an NSSA Autonomous System Boundary Router (ASBR),
this parameter causes it to generate a Type-7 default LSA into the NSSA.
This default provides a route to other areas within the AS for an NSSA ABR,
or to areas outside the AS for an NSSA ASBR.
Command Mode
Router Configuration
Default Setting
No NSSA is configured.
Command Usage
• There are no external routes in an OSPF stub area, so routes cannot be
redistributed from another protocol into a stub area. On the other hand, an
NSSA allows external routes from another protocol to be redistributed into its
own area, and then leaked to adjacent areas.
• This command can be used to simplify administration when connecting a
central site using OSPF to a remote site that is using a different routing
protocol. You can extend OSPF to cover the remote connection by defining
the area between the central router and the remote router as an NSSA.
• All routers in a NSSA must be configured with the same area ID.
• An NSSA is similar to a stub, because when the router is an ABR, it can
send a default route for other areas in the AS into the NSSA using the
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)#
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Open Shortest Path First (OSPF)
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