Microsoft ES4612 User Manual
IP Routing Commands
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area nssa
This command defines a not-so-stubby area (NSSA). To remove an NSSA, use the
no form without any optional keywords. To remove an optional attribute, use the no
form without the relevant keyword.
no form without any optional keywords. To remove an optional attribute, use the no
form without the relevant keyword.
Syntax
[no] area area-id nssa [no-redistribution] [default-information-originate]
• area-id - Identifies the NSSA.
(The area ID must be in the form of an IP address.)
• no-redistribution - Use this keyword when the router is an NSSA Area
Border Router (ABR) and you want the redistribute command to import
routes only into normal areas, and not into the NSSA. In other words, this
keyword prevents the NSSA ABR from advertising external routing
information (learned via routers in other areas) into the NSSA.
routes only into normal areas, and not into the NSSA. In other words, this
keyword prevents the NSSA ABR from advertising external routing
information (learned via routers in other areas) into the NSSA.
• 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 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.
this parameter causes it to generate 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
• 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
• 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.
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.
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.
Type-7 NSSA external routes.
• This router supports up to 16 total areas (either normal transit areas, stubs, or
NSSAs).