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Implementing Routing Policy on Cisco IOS XR Software
Information About Implementing Routing Policy
RC-231
Cisco IOS XR Routing Configuration Guide
OSPF Policy Attach Points
This section describes each of the OSPF policy attach points and provides a summary of the OSPF
attributes and operators.
Default Originate
The default originate attach point allows the user to conditionally inject the default route 0.0.0.0/0 into
the OSPF link-state database, which is done by evaluating the attached policy. If any routes in the local
RIB pass the policy, then the default route is inserted into the link-state database.
The following example shows how to generate a default route if any of the routes that match 10.0.0.0/8
ge 8 le 25 are present in the RIB:
route-policy ospf-originate
if rib-has-route in (10.0.0.0/8 ge 8 le 25) then
pass
endif
end-policy
router ospf 1
default-information originate policy ospf-originate
.
.
.
Redistribute
The redistribute attach point within OSPF injects routes from other routing protocol sources into the
OSPF link-state database, which is done by selecting the route types it wants to import from each
protocol. It then sets the OSPF parameters of cost and metric type. The policy can control how the routes
are injected into OSPF by using the set level command.
The following example shows how to redistribute routes from IS-IS instance instance_10 into OSPF
instance 1 using the policy OSPF-redist. The policy sets the metric type to type-2 for all redistributed
routes. IS-IS routes with a tag of 10 have their cost set to 100, and IS-IS routes with a tag of 20 have
their OSPF cost set to 200. Any IS-IS routes not carrying a tag of either 10 or 20 are not be redistributed
into the OSPF link-state database.
Table 4 Restricted BGP Operations by Attach Point
import export aggregation redistribution
prepend as-path eBGP only eBGP only n/a n/a
set med igp-cost forbidden eBGP only forbidden forbidden
set weight n/a forbidden n/a n/a
suppress forbidden forbidden n/a forbidden