elseif med eq 250 then
set local-preference 110
else
set local-preference 0
endif
The statements within an
if
statement may themselves be
if
statements, as shown in the following example:
if community matches-any (12:34,56:78) then
if med eq 150 then
drop
endif
set local-preference 100
endif
This policy example sets the value of the local preference attribute to 100 on any route that has a community
value of 12:34 or 56:78 associated with it. However, if any of these routes has a MED value of 150, then these
routes with either the community value of 12:34 or 56:78 and a MED of 150 are dropped.
Policy grammar allows user to enter simple if statements with optional else clauses on the same line. However,
the grammar is restricted to single action or disposition statement. For detailed command options, enter match
statement on a separate line.
Note
Boolean Conditions
In the previous section describing the
if
statement, all of the examples use simple Boolean conditions that
evaluate to either true or false. RPL also provides a way to build compound conditions from simple conditions
by means of Boolean operators.
Three Boolean operators exist: negation (
not
), conjunction (
and
), and disjunction (
or
). In the policy language,
negation has the highest precedence, followed by conjunction, and then by disjunction. Parentheses may be
used to group compound conditions to override precedence or to improve readability.
The following simple condition:
med eq 42
is true only if the value of the MED in the route is 42, otherwise it is false.
A simple condition may also be negated using the
not
operator:
not next-hop in (10.0.2.2)
Any Boolean condition enclosed in parentheses is itself a Boolean condition:
(destination in prefix-list-1)
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
405
Implementing Routing Policy
Boolean Conditions