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User Guide for Cisco Security Manager 4.4
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Chapter64 Configuring Routing Policies
OSPF Routing on Cisco IOS Routers
Type 1 versus Type 2 External Routes
Two types of OSPF external routes exist, Type 1 and Type 2. The difference between the two is related
to how the cost (metric) of the route is calculated. The cost of a Type 1 route is the sum of the external
cost and the internal cost used to reach that route. The cost of a Type 2 route is based on the external cost
only. By default, external routes are defined as Type 2. However, a Type 1 route is always preferred over
a Type 2 route to the same destination.
Before You Begin
•Define at least one OSPF process. See Defining OSPF Process Settings, page 64-20.
Related Topics
•Defining OSPF Maximum Prefix Values, page64-23
•Redistributing Routes into OSPF, page 64-22
Step 1 Do one of the following:
•(Device view) Select Platform > Routing > OSPF Process from the Policy selector, then click the
Redistribution tab in the work area.
•(Policy view) Select Router Platform > Routing > OSPF Process from the Policy Type selector.
Select an existing policy or create a new one, and then click the Redistribution tab.
The OSPF Process Redistribution tab is displayed. See Table64-17 on page 64-38 for a description of
the fields on this tab.
Step 2 On the OSPF Process Redistribution tab, select a row from the OSPF Redistribution Mappings table,
then click Edit, or click Add to create a mapping. The OSPF Redistribution Mapping dialog box is
displayed. See Table 64-18 on page 64-40 for a description of the fields in this dialog box.
Step 3 Select an existing OSPF process from the displayed list.
Step 4 Select the protocol whose routes you want to redistribute into the selected OSPF process.
Note You can create a single mapping for each static route, RIP route, BGP AS, EIGRP AS, and OSPF
process.
Step 5 (Optional) Modify the default metric (cost) of the redistributed routes. The metric determines the priority
of the routes.
Step 6 Select the Metric Type of external route to create, Type 1 or Type 2. The default is Type 2.
Step 7 (Optional) Select the Limit to Subnets check box to redistribute only subnetted routes. By default, this
option is not selected.
Step 8 Click OK to save your definitions. The redistribution mapping appears in the Redistribution Mapping
table on the OSPF Process Redistribution tab.
Defining OSPF Maximum Prefix Values
You can define a maximum number of prefixes (routes) that may be redistributed from other protocols
or OSPF processes into a selected OSPF process. Setting a limit helps prevent the router from being
flooded by too many redistributed routes. For example, without a defined maximum, flooding can occur
when BGP is redistributed into OSPF.