SMC Networks SMC6724L3 manual 259

IP ROUTING COMMANDS

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-originatekeyword. 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-originatekeyword.

•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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