ECS4660-28F_Management Guide-R03

C HAPTER 51 | IP Routing Commands
Open Shortest Path First (OSPFv3)
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Area Configuration
area stub This command defines a stub area. To remove a stub, use the no form
without the optional keyword. To remove the summary attribute, use the
no form with the summary keyword.
SYNTAX
[no] area area-id stub [no-summary]
area-id - Identifies the stub area. The area ID can be in the form of
an IPv4 address or as a four octet unsigned integer ranging from
0-4294967295.
no-summary - Stops an Area Border Router (ABR) from sending
summary link advertisements into the stub area.
COMMAND MODE
Router Configuration
DEFAULT SETTING
No stub is configured.
Summary advertisement are sent into the stub.
COMMAND USAGE
◆ All routers in a stub must be configured with the same area ID.
◆ Routing table space is saved by stopping an ABR from flooding Type-4
Inter-Area Router and Type 5 AS-External LSAs into the stub. Since no
information on external routes is known inside the stub, an ABR will
advertise the default route 0::0/0 using a Type 3 Inter-Area Prefix LSA.
◆ The default setting for this command blocks Type-4 Inter-Area Router
and Type 5 AS-External LSAs. Therefore, any destinations that cannot
be matched to an inter-area or intra-area route will have to use the
default route.
◆ Use the no-summary parameter of this command on an ABR attached
to the stub to define a totally stubby area, blocking all Type 3 network
summary LSAs. Define an area as a totally stubby area only if routers
in the area do not require summary LSAs from other areas.
◆ Use the area default-cost command to specify the cost of a default
summary route sent into a stub by an ABR attached to the stub area.
EXAMPLE
This example creates a stub area 2, and makes it totally stubby by blocking
all Type 3 summary LSAs.
Console(config-router)#area 2 stub no-summary
Console(config-router)#