C
ONFIGURING

THE

S

WITCH

3-208

CLI - This example configures the backbone area and one transit area.

Configuring Summary Addresses (for External AS Routes)

An Autonomous System Boundary Router (ASBR) can redistribute routes
learned from other protocols into all attached autonomous systems. (See
“Redistributing External Routes” on page 3-210) To reduce the amount of
external LSAs imported into your local routing domain, you can configure
the router to advertise an aggregate route that consolidates a broad range
of external addresses.
Command Usage
If you are not sure what address ranges to consolidate, first enable
external route redistribution via the Redistribute Configuration screen,
view the routes imported into the routing table, and then configure one
or more summary addresses to reduce the size of the routing table and
consolidate these external routes for advertising into the local domain.
To summarize routes sent between OSPF areas, use the Area Range
Configuration screen (page 3-196).
Console(config-router)#network 10.0.0.0 255.0.0.0
area 0.0.0.0 4-255
Console(config-router)#network 10.1.1.0 255.255.255.0 area 0.0.0.1
Console(config-router)#end
Console#show ip ospf 4-271
Routing Process with ID 10.1.1.253
Supports only single TOS(TOS0) route
Number of area in this router is 4
Area 0.0.0.0 (BACKBONE)
Number of interfaces in this area is 1
SPF algorithm executed 8 times
Area 0.0.0.1
Number of interfaces in this area is 1
SPF algorithm executed 5 times
Area 0.0.0.2 (STUB)
Number of interfaces in this area is 1
SPF algorithm executed 13 times
Area 0.0.0.3 (NSSA)
Number of interfaces in this area is 1
SPF algorithm executed 12 times
Console#