A compound condition takes either of two forms. It can be a simple expression followed by the
and
operator,
itself followed by a simple condition:
med eq 42 and next-hop in (10.0.2.2)
A compound condition may also be a simpler expression followed by the
or
operator and then another simple
condition:
origin is igp or origin is incomplete
An entire compound condition may be enclosed in parentheses:
(med eq 42 and next-hop in (10.0.2.2))
The parentheses may serve to make the grouping of subconditions more readable, or they may force the
evaluation of a subcondition as a unit.
In the following example, the highest-precedence
not
operator applies only to the destination test, the
and
operator combines the result of the
not
expression with the community test, and the
or
operator combines
that result with the MED test.
med eq 10 or not destination in (10.1.3.0/24) and community matches-any ([12..34]:[56..78])
With a set of parentheses to express the precedence, the result is the following:
med eq 10 or ((not destination in (10.1.3.0/24)) and community matches-any
([12..34]:[56..78])
The following is another example of a complex expression:
(origin is igp or origin is incomplete or not med eq 42) and next-hop in (10.0.2.2)
The left conjunction is a compound condition enclosed in parentheses. The first simple condition of the inner
compound condition tests the value of the origin attribute; if it is Interior Gateway Protocol (IGP), then the
inner compound condition is true. Otherwise, the evaluation moves on to test the value of the origin attribute
again, and if it is incomplete, then the inner compound condition is true. Otherwise, the evaluation moves to
check the next component condition, which is a negation of a simple condition.
apply
As discussed in the sections on policy definitions and parameterization of policies, the
apply
command
executes another policy (either parameterized or unparameterized) from within another policy, which allows
for the reuse of common blocks of policy. When combined with the ability to parameterize common blocks
of policy, the
apply
command becomes a powerful tool for reducing repetitive configuration.
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
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Implementing Routing Policy
apply