[AUDIO LOGO]
So now that we mostly have IS-IS up and running
in our environment, let's take a look
at a few last little topics.
First, we'll take a look at summarization in IS-IS.
Remember that much like OSPF, it's
very limited as to where we can summarize.
Then we'll take a quick look at some filtering.
And we'll wrap up with doing some redistribution
from, well, in this case, BGP into IS-IS.
So again, let's take a quick look at our topology
just to remember what we're going to be setting up.
And then we'll jump into the command line
and get these features up and running.
So to start off with, we're going
to look at router-5's loopback as it gets advertised over
towards router-1, and we're going
to summarize this on router-2.
We'll then follow up with summarizing it
on router-4 as well because otherwise, of course,
the non-summarized route would come through the bottom
and get leaked out through router-3.
After that, we'll also look at how to summarize on IOS XE.
So we'll also summarize here on router-8
as routes are being sent into Area 100.
So we'll see it on both platforms.
Then we'll do a little bit of filtering.
We'll filter some of the routes that are coming from Area 100
into Area 20.
And then we'll wrap up with doing some redistribution
from BGP into IS-IS up here on router-6.
So again, we'll start off with our summarization.
Let's jump into the command line on router-2.
Actually, before we jump on router-2
and do the summarization, let's first verify
what the route currently looks like on router-1.
So let's do a show IP route for 10.5.5.5.
And what we see here is that we do
have a slash 32 entry for this loopback,
known, of course, via IS-IS-1.
And this is, in fact, learned from router-2.
So now, let's go over to router-2
and do our summarization.
So to do this, we simply go into the router IS-IS process
under the address-family.
And we use the command summary-prefix.
After this, it simply wants the prefix.
So we're going to summarize this to a slash 24.
And then it has a few options.
We want to summarize this as it goes into level-2.
And then if we want, we can put a tag on it.
We'll just tag it as a 2 since it is,
in fact, coming from router-2.
Let's go ahead and commit those changes.
And let's hop back over to router-1.
So if we look at this same command,
again, on router-1, notice that it's now
showing it as multipathing.
It's actually going to go through router-2 and router-3,
but notice that the routes aren't actually from router-2.
Both of these entries are from router-4.
So router-2 is no longer advertising the slash 32.
If we, instead, ask for the address of the slash 24,
now, we see that this is the summarized route that's
coming from router-2.
Now, it can be useful in certain situations
to only summarize on one router on the edge of an area.
For example, we could use this to manipulate
the flow of traffic going into that area
by leaking longer prefixes to one router than the other.
This is not a very common thing to do,
but it certainly could be done.
Normally, when we're summarizing,
the idea is to summarize this route into the whole rest
of the network.
And as such, we would want to make
sure we're summarizing the same on all the routers
at the edge of that area.
In our case, that's routers 2 and 4.
So let's go ahead and jump over to router-4
and do our summarization there as well.
So on router-4, again, it's into router IS-IS-1,
address-family IPv4.
We'll set the summary-prefix to the 10.5.5.0 slash 24
into level-2.
And this time, we'll tag it with a 4.
Let's go verify on router-1, again.
So if we take a look at this again,
we can see that whether we enter the command now
for the slash 24 or for the slash 32,
notice that both of these are now giving us
the same route, the slash 24 route, going to router 2,
which we can also tell because we see here
that it also has that tag of 2 along with the entry.
Now, if we were to do a show IP route IS-IS,
notice that router-8's loopback is also a slash 32.
Well, what if we wanted to summarize on IOS XE?
Well, let's go over and take a look at router-8.
So we'll go into configuration mode,
again, into our IS-IS process.
And it's almost the same command.
Instead of summary-prefix, it's summary-address.
And another difference is, notice,
it first wants the address.
So we'll again say 10.8.8.0.
And then it actually wants the subnet mask written out
in decimal format.
So we can't use slash notation here for our prefix length.
After that, we have the same options.
So we could say that this, again, is level-2.
Minor difference here is we have the dash between level and 2
rather than a space.
We can still tag it.
This is done the exact same way.
So we could say tag 8.
And if we want, we can also set a metric on it.
So maybe we want to set a metric.
We could say metric 100, for example.
We'll exit out of configuration.
And now, let's go look at this route on router-1, again.
So once again, we'll do a show IP route IS-IS.
First, we see that the 10.8.8.8 is gone,
and we now have our slash 24 instead.
If we look at the detail on that route,
first, we see that the metric is definitely
above just having a 10 on each interface given
that it's only a few hops away.
So the 120 indicates that it's definitely
setting that metric to 100.
Plus, it looks like two lengths away
because we haven't really changed the IS-IS metrics
on our interfaces at this point.
And we also see that it has that tag of 8
that we set as we brought the route in.
Now, something else we could do along the same lines
here is we can filter.
So let's go back over to router-8.
Here, we'll just do a show IP route IS-IS.
And one thing we can note is that we
have a lot of 50 prefixes here.
We don't need those.
So let's say we want to filter them out on router-8.
All we have to do is go into configuration mode.
We'll make an IP prefix list.
We'll call it something like PL underscore IS-IS filter.
And we'll start with a deny of--
and we'll just deny everything that starts with a 50.
So we'll say 50.0.0.0 slash 8, less than or equal to 32.
So all subnets of it as well.
Then of course, we have to allow everything else.
That will permit everything else.
Then we simply go into our routing process.
We say, distribute list.
Notice that we can actually use access lists
for this or even a route map, but we wrote a prefix list.
So we'll do it with a prefix list.
And again, it's PL underscore IS-IS filter.
And we want to do this as the routes are
coming in to the IS-IS process.
We'll exit our configuration.
We'll do a show IP route IS-IS, again.
And notice now, all of the 50 routes
are gone out of our routing table.
So filtering in IS-IS is just that easy.
One last thing we want to look at here
is redistributing into IS-IS.
And we'll see that this is just as easy as the summarization
and the filtering.
So let's jump up to router-6, and we're
going to do some redistribution from BGP into IS-IS.
So on router-6, if we say show IP route BGP,
first thing to note is the only BGP route or prefix
that we're learning is router-10's loopback.
Well, that's fine.
We don't need a whole lot here.
What we want to do is simply go into configuration mode,
into the IS-IS process.
All we have to do is say BGP and then put in the AS number.
In our demonstration here, the AS number is 100.
And note that there's other options.
We can, of course, choose whether we want to redistribute
just into certain levels.
We could set the metrics on these.
We could, again, go through a route map
to manipulate updates and/or filter.
So there's a lot of more advanced options
here that we'll look at a little bit more
in our redistribution skills.
But for now, we'll just go ahead and hit Enter
to do a basic redistribution.
We'll exit out of configuration.
And let's go see what this looks like on another router.
Let's say, router-7.
So here on router-7, if we do a show IP route IS-IS,
first thing to note is that we do, in fact, now
have router-10's loopback.
It's right here, is a slash 32, being learned
as an IS-IS level-2 update.
But what if we look at the detail on that?
Let's do a show IS-IS rib, and we'll
ask for that particular prefix.
The main thing we want to see here
is notice on the prefix attributes.
The X flag is now set because this is a redistributed prefix.
In this video, we took a look at some little features in IS-IS.
We started off by looking at summarization between areas,
then we took a look at how to do a little bit of filtering.
And finally, we wrapped up with just
doing a simple redistribution into IS-IS
in this example from BGP.
I hope this has been informative for you,
and I'd like to thank you for viewing.