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[AUDIO LOGO]

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To wrap up this section,
let's take a look

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at some of the advanced
features of RPL.

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We'll look at things like
nesting, parameterization,

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and creating and
configuring sets that we

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can use in our policies.

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So we'll look at a
couple of things here.

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We'll also jump on to
the command line, just

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a little bit, and take a look at
things like editing our policy

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once it's been written.

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So let's jump in and take a
look at some of these details.

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And then, again, we'll wrap up
by looking at some verification

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and editing commands.

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So let's start off by
talking about nesting.

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So we do have basically two ways
of doing some advanced nesting

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here.

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First, is we can
have nested policies.

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In this example,
what we're doing is

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we're writing two
different policies.

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One is called RP_SET_MED, the
other is called RP_AS_PATH.

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And then we have another
policy, in this case,

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we're just calling it RP_PARENT.

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And you can see what
we're doing here

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is we're applying these
other two policies, which

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means that whatever
these are set to do

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are going to be done in
this policy down here.

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So this is simply
nesting policies.

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We can also nest If statements.

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This one's actually
a little bit easier.

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We simply have an
If statement that

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says, for example, if
the med equals 100, then

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if the local preference is
greater than or equal to 200,

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then set the
community to 100:200

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and we're doing it additively.

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But we're simply
saying, essentially,

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if this and this, then do this.

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That's essentially
what this is saying.

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The next feature we want to
look at is parameterization.

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This can be set in
one of two ways.

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The first of which is globally.

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And the way this works is
we use this special policy

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called policy global.

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Under this, we
then create entries

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with values that are
separated by commas,

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and we can just simply
put in multiple entries.

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So, essentially, we're
defining variables.

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Once we've defined
everything that we want to,

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we then simply say end global
to exit that configuration mode.

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Then we write our policy.

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In this case, we're doing
something called RP_SET_MED.

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And we're simply saying, if
the AS path originates from AS,

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and you can see the
way we call to this?

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Is we put them in single
quotes, and we use dollar sign,

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and then we call to the
global parameter that we set.

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And it'll then take this
value, in this case, a 65001

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and plug it into
the statement there.

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Then we say to set
the Med to DF_MED.

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This, of course,
matches this parameter.

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So it's going to take the
300, and plug it in down here.

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So this is how we set
these parameters globally.

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Again, very much
like using variables.

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The big advantage
to this, of course,

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is we only have to configure
these parameters once globally,

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and then we can call to
them from as many policies

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as we need to write.

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So we can reuse these as
many times as we need to.

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The other choice
is that they can

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be passed into a nested policy.

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So let's take a look
at this example.

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So here we have a policy
called RP_SET_MED.

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And this is looking to receive
two parameters, $MED and $AS.

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Now, these parameters
are going to be passed

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into these parts of the policy.

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The way those values are sent
in is shown here at the bottom.

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So here we have a policy
called RP_UPDATES,

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and it's got some If statements,
but then look what it's doing.

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It seemed to apply
the RP_SET_MED,

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and it's specifying the value
for Med, and the value for AS.

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So these values are then
passed into these parameters

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and used in the policy
shown at the top.

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We also have an
else If down here

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where we call to the same policy
and set different parameters

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to it.

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So when the policy
gets called here,

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it's going to be sent
different values.

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So this is how the parameters
can be passed from a parent

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policy into a nested policy.

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Next let's take a
look at value sets.

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These can either
be inline or named.

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We have five different types of
named sets that are available.

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We have an AS-path
set, a community set,

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an extended community set,
prefix set, and a route

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distinguisher your set.

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These are the things
that are available.

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We'll be looking at these
in a little bit more detail

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in just a moment.

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But first, let's look
at some examples.

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So here we have an inline
example where we're simply

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saying if the attribute
is in, and then

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we simply list out
multiple values.

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So we're defining
the set right here.

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That is the set.

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So if whatever it
is we're looking for

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is in any of these
values, then do whatever.

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Very, very simple.

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We're defining a set right
there on the If statement.

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More commonly what we
will do is actually create

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some form of a named set.

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Now, first, let's just
reference our little note here

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that the x set over
here on the left

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is referring to one
of those types of sets

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that we talked about as
already being available.

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So an AS-path set, community
set, extended community set,

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prefix set, or a route
distinguisher set or RD set.

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So we're simply not showing
an example of all of them,

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but they all have the
same basic formatting.

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After you define
the type, you then

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give it a name of some
sort, and then you

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list the different
values, separated, again,

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by commas at the
end of each line.

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You then say end set to
exit set configuration.

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Then when we want to
use this, we simply

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call to it by its name.

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So let's talk a
little bit about some

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of the different types of sets.

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We'll start with
the AS path set.

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Essentially, we can use either
an IOS regular expression.

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We can use a DFA
regular expression,

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which is the deterministic
finite automa or automation.

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This isn't used very commonly,
at least not in my experience,

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but it is another option.

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This can use the
neighbor-is statement,

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originates-from statement,
passes-through statement,

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or the length statement.

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So quite a few
different options we

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have here when trying
to match on the AS.

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Of course, a very,
very common one

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is the IOS regex where we use
regular expressions to match

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on our AS path sets.

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Community and extended
community sets

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can also use IOS regular
expressions, the DFA

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regular expressions, except
its own, internet, local AS,

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no advertise, no
export or private AS,

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which of course, would
include the private AS range.

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So those are the options for
both community and extended

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community sets.

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Now, when you're actually
matching on those,

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we have different
types of matching.

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You can do a match-any,
a match-every,

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which of course, is an all.

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Any would be an or.

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You can also do a
matches-within, which

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means all the
communities on the routes

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have to be within
the match element,

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but they don't have
to be an exact match.

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Finally, we have prefix sets.

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These are almost the
same as prefix-lists.

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However, in addition
to supporting less than

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or equal to and greater
than or equal to,

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these also support equals, which
as we know prefix lists do not.

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So the last thing
we want to look at

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is actually editing
an existing policy.

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Now, the interesting
thing with this

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is if you go into
configuration mode

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and you actually
go into a policy

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that you've already written,
it will delete that policy

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and you'll have to rewrite it.

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It overwrites the
existing policy.

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So clearly, this is not a
really good editing tool.

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So this, of course,
can be done but you're

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going to be re-entering
the entire policy.

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Now, if you have that policy
in something like a text editor

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and you're just
pasting it back in,

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well that's really
not a big deal.

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But if you're just writing the
policy manually on the CLI,

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that could, of
course, be an issue.

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So instead, what we want to
do is actually edit the list.

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So the best way to do this.

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Let's jump over to
the command line,

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and take a look at how to
edit an existing policy.

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So we'll just do this
here on router 1.

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Let's start off with a show RPO.

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And we can see that this
already has a policy.

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It's simply called
all, and all it's doing

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is passing all the routes.

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So, obviously, not a very
complex policy, but it

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doesn't matter how complex it
is to see how to edit this.

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So what we do is we
say edit route-policy,

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and we put in the name.

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In this case, it's all.

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And what you want to see here
is that there are three choices

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that we can use to edit this.

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All three of these
are, of course,

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rather well known
Linux-based text editors.

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You can choose whichever one
you're the most familiar with.

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Personally, I usually
use Nano or Vim.

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So let's just take
a look at Nano.

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And as we can see, it simply
opens the file in Nano.

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And we could edit
this however we want.

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So if I wanted to, I could
change the pass to a drop,

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and then we could hit
Control O to write this out.

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It's going to ask what do
we want to name the file.

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Keep the default because
this is what the system is

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using in the background.

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So hit Enter.

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We'll hit Control X to exit.

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It's going to ask if we
want to commit, of course,

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we're going to say yes.

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Fortunately, I'm not using
that policy for anything

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on this system right now.

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Let's do a show RPL again.

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And we can see that
policy now says drop.

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So it's that easy.

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It's just like editing
any other text file using

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one of these text editors.

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Now, the downside,
of course, to this is

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don't have context
sensitive help.

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You're on your own just writing
the policy in the text editor.

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Now, two other
useful commands you

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might want to be aware
of in relation to RPL

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is if we do our show RPL
again, and we say route-policy,

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ask for the name of our policy
again, we can say detail.

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Now, in this case, it doesn't
really change anything,

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but on a more complex
policy and a policy that's

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actually in use, you would get
more information out of this.

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And another good command is
to say attachment points.

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This will tell you where the
policy is actually being used.

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And as I mentioned before,
this particular policy

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is not being used on
this device at this time.

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So it's not attached
to any attached point.

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We'll review these
commands as we get more

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into other parts of the course,
and we start using RPL more

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in other sections.

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So in this video, we
took a look at some

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of the more advanced
features of RPL,

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including our nesting,
our parameterization,

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setting up sets,
and editing a policy

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without having to rewrite the
whole thing in configuration

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mode.

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I hope this has been
informative for you,

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and I'd like to thank
you for viewing.

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