Cisco ASR 9000 Series Routing Configuration Manual page 584

Routing Policy Language Overview
Drop Everything Policy
The following example shows how the policy explicitly rejects all routes presented to it. This type of policy
is used to ignore everything coming from a specific peer.
route-policy quickstart-drop
drop
end-policy
Ignore Routes with Specific AS Numbers in the Path
The following example shows the policy definition in three parts. First, the as-path-set command defines
three regular expressions to match against an AS path. Second, the route-policy command applies the AS
path set to a route. If the AS path attribute of the route matches the regular expression defined with the
as-path-set command, the protocol refuses the route. Third, the route policy is attached to BGP neighbor
10.0.1.2. BGP consults the policy named ignore_path_as on routes received (imported) from neighbor 10.0.1.2.
as-path-set ignore_path
ios-regex '_11_',
ios-regex '_22_',
ios-regex '_33_'
end-set
route-policy ignore_path_as
if as-path in ignore_path then
drop
else
pass
endif
end-policy
router bgp 2
neighbor 10.0.1.2 address-family ipv4 unicast policy ignore_path_as in
Set Community Based on MED
The following example shows how the policy tests the MED of a route and modifies the community attribute
of the route based on the value of the MED. If the MED value is 127, the policy adds the community 123:456
to the route. If the MED value is 63, the policy adds the value 123:789 to the community attribute of the route.
Otherwise, the policy removes the community 123:123 from the route. In any case, the policy instructs the
protocol to accept the route.
route-policy quickstart-med
if med eq 127 then
set community (123:456) additive
elseif med eq 63 then
set community (123:789) additive
else
delete community in (123:123)
endif
pass
end-policy
Set Local Preference Based on Community
The following example shows how the community-set named quickstart-communities defines community
values. The route policy named quickstart-localpref tests a route for the presence of the communities specified
in the quickstart-communities community set. If any of the community values are present in the route, the
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
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Implementing Routing Policy