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IP R
OUTING
3-293
Command Usage
• Before you create a stub or NSSA, first specify the address range for
an area using the Network Area Address Configuration screen
(page 3-305).
• 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 you set the default cost 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 you use the
“NoSummary” option to also block Type-3 summary LSAs that
advertise the default route for destinations external to the local
area or the AS, the stub will become completely isolated.
Note: This router supports up to 16 total areas (either normal transit
areas, stubs, or NSSAs).