Cisco ASR 9000 Series Routing Configuration Guide

The parameterized policy param-example provides a policy definition that is expanded with the values provided
as the parameters in the neighbor route-policy in and out statement.
Global Parameterization
RPL supports the definition of systemwide global parameters that can be used inside policy definition. Global
parameters can be configured as follows:
Policy-global
glbpathtype ‘ebgp’
glbtag ‘100’
end-global
The global parameter values can be used directly inside a policy definition similar to the local parameters of
parameterized policy. In the following example, the globalparam argument, which makes use of the global
parameters gbpathtype and glbtag, is defined for a nonparameterized policy.
route-policy globalparam
if path-type is $glbpathtype then
set tag $glbtag
endif
end-policy
When a parameterized policy has a parameter name “collision” with a global parameter name, parameters
local to policy definition take precedence, effectively masking off global parameters. In addition, a validation
mechanism is in place to prevent the deletion of a particular global parameter if it is referred by any policy.
Semantics of Policy Application
This section discusses how routing policies are evaluated and applied. The following concepts are discussed:
Boolean Operator Precedence
Boolean expressions are evaluated in order of operator precedence, from left to right. The highest precedence
operator is NOT, followed by AND, and then OR. The following expression:
med eq 10 and not destination in (10.1.3.0/24) or community matches-any ([10..25]:35)
if fully parenthesized to display the order of evaluation, would look like this:
(med eq 10 and (not destination in (10.1.3.0/24))) or community matches-any ([10..25]:35)
The inner NOT applies only to the destination test; the AND combines the result of the NOT expression with
the Multi Exit Discriminator (MED) test; and the OR combines that result with the community test. If the
order of operations are rearranged:
not med eq 10 and destination in (10.1.3.0/24) or community matches-any ([10..25]:35)
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
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Implementing Routing Policy
Semantics of Policy Application

Cisco ASR 9000 Series Specifications

General

Brand	Cisco
Model	ASR 9000 Series
Category	Network Router
Language	English