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Command Line Interface
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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 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.
area virtual-link
This command defines a virtual link. To remove a virtual link, use the no form with no
optional keywords. To restore the default value for an attribute, use the no form with
the required keyword.
Syntax
[no] area area-id virtual-link router-id
[authentication [message-digest | null ]] [hello-interval seconds]
[retransmit-interval seconds] [transmit-delay seconds] [dead-interval
seconds] [[authentication-key key] | [message-digest-key key-id md5
key]]
no area area-id
• area-id - Identifies the transit area for the virtual link.
(The area ID must be in the form of an IP address.)
• router-id - Router ID of the virtual link neighbor. This must be an Area
Border Router (ABR) that is adjacent to both the backbone and the transit
area at the other end of the virtual link.
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)#