Command Usage
• Before you create the backbone, a stub or NSSA, first specify the address range
for the area using the Network Area Address Configuration screen (page 20-31).
• 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 e xit
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 f or an n orm al area , stu b or NS SA . The area ID m ust be in th e
form of an IPv4 address.
• Area T ype – Sp ecifies a normal area, stub area, or not-so-s tubby are a (NSS A).
Area ID 0.0.0.0 is set to the backbone by default. (Default : Norma l area)
• Default Cost – Cost for the default summary route sent into a stub from an ar ea
border router (ABR). (Range: 0-16777215; Default: 1)
- Note that if you set the default cost to “0,” the router will not advert ise a de fault
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 sum mary
LSAs and Type 5 external LSAs. If you use the “NoSumma ry ” o ption t o also block
Type-3 summary LSAs that advertise the default route for dest ination s exter nal to
the local area or the AS, the stub will become completely isolate d.
Define an area as a totally stubby area only if rout ers in the area do not requ ire
summary LSAs from other areas.
Note:
This router supports up to 16 total areas (either normal transit areas, stubs, or
NSSAs).
20-21
Configuring the Open Shortest Path First Protocol
20