Configuring the ECN330-switch
444 1553-KDU 137 365 Uen D 2006-06-16
• Routes that can be advertised with NSSA external LSAs include
network destinations outside the AS learned through OSPF, the default
route, static routes, routes derived from other routing protocols such as
RIP, or directly connected networks that are not running OSPF.
• 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.
Default Cost – This specifies a cost for the default summary route sent into a
stub or not-so-stubby area (NSSA) from an Area Border Router (ABR).
Command Usage
• Before creating a stub or NSSA, first specify the address range for an
area using the Network Area Address Configuration screen (page 442).
• Stubs and NSSAs cannot be used as a transit area, and should
therefore be placed at the edge of the routing domain.
• A stub or NSSA can have multiple ABRs or exit points. However, all of
the exit points and local routers must contain the same external routing
data so that the exit point does not need to be determined for each
external destination.
Command Attributes
• Area ID – Identifier for an area, stub or NSSA.
• Area Type – Specifies a normal area, stub area, or not-so-stubby area
(NSSA). Area ID 0.0.0.0 is set to the backbone by default. (Default:
Normal area)
• Default Cost – Cost for the default summary route sent into a stub from
an area border router (ABR). (Range: 0-16777215; Default: 1)
• Note that if the default cost is set to “0,” the router will not advertise
a default route into the attached stub.
•
Summary
– Makes an ABR send a Type-3 summary link advertisement
into a stub.
(Default: Summary)
• A stub is designed to save routing table space by blocking Type-4
AS summary LSAs and Type-5 external LSAs. If the “NoSummary”
option is also used to block Type-3 summary LSAs that advertise
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