Edge-Core AS5700-54X, Cli Reference Manual, Page: 852 / 1116

Chapter 29
| IP Routing Commands
Open Shortest Path First (OSPFv2)
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type-value
1 - Type 1 external route
2 - Type 2 external route (default) - Routers do not add internal cost to
the external route metric.
Command Mode
Router Configuration
Default Setting
No NSSA is configured.
Command Usage
◆
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 BGP or 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)#