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Open Shortest Path First (OSPFv2 and OSPFv3) | 711
Configure stub areas
OSPF supports different types of LSAs to help reduce the amount of router processing within the areas.
Type 5 LSAs are not flooded into stub areas; the Area Border Router (ABR) advertises a default route into
the stub area to which it is attached. Stub area routers use the default route to reach external destinations
To ensure connectivity in your OSPFv2 network, never configure the backbone area as a stub area.
Use these commands in the following sequence, starting in EXEC Privilege mode to configure a stub area.
Use the
show ip ospf database process-id database-summary command syntax (Figure 413) in the
EXEC Privilege mode To view which LSAs are transmitted.
Figure 32-12. Command Example: show ip ospf process-id database database-summary
To view information on areas, use the show ip ospf process-id command in the EXEC Privilege mode.
Step Command Syntax Command Mode Usage
1
show ip ospf process-id [vrf
vrf name] database
database-summary
EXEC Privilege Review all areas after they were configured to
determine which areas are NOT receiving type 5
LSAs.
vrf name: Show only the OSPF information tied to the
VRF process.
2
configure
EXEC Privilege Enter the CONFIGURATION mode.
3
router ospf process-id [vrf {vrf
name}]
CONFIGURATION Enter the ROUTER OSPF mode.
Process ID is the ID assigned when configuring
OSPFv2 globally (page 58).
vrf name: Enter the VRF key word and instance name to
tie the OSPF instance to the VRF. All network commands
under this OSPF instance are subsequently tied to the
VRF instance.
4
area area-id stub
[no-summary]
CONFIG-ROUTER-O
SPF-id
Configure the area as a stub area. Use the
no-summary keywords to prevent transmission in
to the area of summary ASBR LSAs.
Area ID is the number or IP address assigned when
creating the Area (page 60).
FTOS#show ip ospf 34 database database-summary
OSPF Router with ID (10.1.2.100) (Process ID 34)
Area ID Router Network S-Net S-ASBR Type-7 Subtotal
2.2.2.2 1 0 0 0 0 1
3.3.3.3 1 0 0 0 0 1
FTOS#