Configuring Route Summarization Between Ospf Areas - Cisco Catalyst 6500 Series Configuration Manual

Chapter 8 Configuring IP Addresses, Routing, and DHCP
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Configuring Route Summarization Between OSPF Areas

Single context mode only
Routed firewall mode only
Route summarization is the consolidation of advertised addresses. This feature causes a single summary
route to be advertised to other areas by an area boundary router. In OSPF, an area boundary router
advertises networks in one area into another area. If the network numbers in an area are assigned in a
way such that they are contiguous, you can configure the area boundary router to advertise a summary
route that covers all the individual networks within the area that fall into the specified range.
To define an address range for route summarization, follow these steps:
Step 1 If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
FWSM(config)# router ospf process_id
Step 2 To set the address range, enter the following command:
FWSM(config-router)# area area-id range ip-address mask [advertise | not-advertise]
This example shows how to configure route summarization between OSPF areas:
FWSM(config)# router ospf 1
FWSM(config-router)# area 17 range 12.1.0.0 255.255.0.0
OL-6392-01
To summarize groups of addresses, enter the following command:
FWSM(config-router)# summary address ip_address mask [not advertise] [tag tag ]
This command helps reduce the size of the routing table. Using this command for OSPF causes an
OSPF autonomous system boundary Router (ASBR) to advertise one external route as an aggregate
for all redistributed routes that are covered by the address.
OSPF does not support summary-address 0.0.0.0 0.0.0.0.
In the following example, the summary address 10.1.0.0 includes address 10.1.1.0, 10.1.2.0,
10.1.3.0, and so on. Only the address 10.1.0.0 is advertised in an external link-state advertisement:
FWSM(config-router)# summary-address 10.1.1.0 255.255.0.0
Before you use this feature, consider these guidelines:
You can set a type 7 default route that can be used to reach external destinations. When
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configured, the router generates a type 7 default into the NSSA or the NSSA area boundary
router.
Every router within the same area must agree that the area is NSSA; otherwise, the routers will
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not be able to communicate.
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
Configuring OSPF
8-13