Configuring Route Summarization Between Ospf Areas; Configuring Route Summarization When Redistributing Routes Into Ospf - Cisco FirePOWER ASA 5500 series Configuration Manual

Configuring OSPF

Configuring Route Summarization Between OSPF Areas

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, perform the following steps:
If you have not already done so, enter the router configuration mode for the OSPF process you want to
Step 1
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2 To set the address range, enter the following command:
hostname(config-router)# area area-id range ip-address mask [advertise | not-advertise]
The following example shows how to configure route summarization between OSPF areas:
hostname(config)# router ospf 1
hostname(config-router)# area 17 range 12.1.0.0 255.255.0.0

Configuring Route Summarization When Redistributing Routes into OSPF

When routes from other protocols are redistributed into OSPF, each route is advertised individually in
an external LSA. However, you can configure the security appliance to advertise a single route for all
the redistributed routes that are covered by a specified network address and mask. This configuration
decreases the size of the OSPF link-state database.
Cisco Security Appliance Command Line Configuration Guide
9-14
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:
hostname(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
–
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
–
not be able to communicate.
Chapter 9 Configuring IP Routing
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