Laptop User Manual

Implementing Routing Policy on Cisco IOS XR Software
Information About Implementing Routing Policy
RC-224
Cisco IOS XR Routing Configuration Guide
Note The protocol configuration rejects attempts to attach policies that perform unsupported operations.
The following sections describe the protocol attach points, including information on the attributes
(commands) and operations that are valid for each attach point.
• BGP Policy Attach Points, page RC-224
• OSPF Policy Attach Points, page RC-231
• OSPFv3 Policy Attach Points, page RC-232
• IS-IS Policy Attach Points, page RC-234
See the Cisco IOS XR Routing Command Reference for more information on the attributes and
operations.
BGP Policy Attach Points
This section describes each of the BGP policy attach points and provides a summary of the BGP
attributes and operators.
Aggregation
The aggregation attach point generates an aggregate route to be advertised based on the conditional
presence of subcomponents of that aggregate. Policies attached at this attach point are also able to set
any of the valid BGP attributes on the aggregated routes. For example, the policy could set a community
value or a MED on the aggregate that is generated. The specified aggregate is generated if any routes
evaluated by the named policy pass the policy. More specifics of the aggregate are filtered using the
suppress-route keyword. Any actions taken to set attributes in the route affect attributes on the
aggregate.
In the policy language, the configuration is controlled by which routes pass the policy. The suppress map
was used to selectively filter or suppress specific components of the aggregate when the summary-only
flag is not set. In other words, when the aggregate and more specific components are being sent, some
of the more specific components can be filtered using a suppress map. In the policy language, this is
controlled by selecting the route and setting the suppress flag. The attribute-map allowed the user to set
specific attributes on the aggregated route. In the policy language, setting attributes on the aggregated
route is controlled by normal action operations.
In the following example, the aggregate address 10.0.0.0/8 is generated if there are any component routes
in the range 10.0.0.0/8 ge 8 le 25 except for 10.2.0.0/24. Because summary-only is not set, all
components of the aggregate are advertised. However, the specific component 10.1.0.0 are suppressed.
route-policy sample
if destination in (10.0.0.0/8 ge 8 le 25) then
set community (10:33)
endif
if destination in (10.2.0.0/24) then
drop
endif
if destination in (10.1.0.0/24) then
suppress-route
endif
end-policy