In this video, we're going to take a look
at some places in the network based
on the routing protocols where we can implement and verify
summarization.
And let's use this topology to discuss summarization.
Summarization is fantastic if it happens correctly.
So let's imagine in this network that we've got over here
on this part of our network all the addresses start with 10.1.
something.
And we'll just go ahead and do a slash 16 there.
And over here on this side, I'll put it
in a slightly different color.
Everything over here is 10.2. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Everything over here is 10.2.
something slash 16.
And then up here, it's 10.0.
So depending on the type of routing protocol
that we're running, we have different options
for summarization.
If we're running OSPF, for OSPF if we want to do summarization
we need to be an ABR, an Area Border Router, who
can summarize between areas, or we
need to be an a ASBR, an Autonomous System Boundary
Router, who's redistributing routes in,
which is a-whole-nother set of possible troubleshooting.
But assuming we're bringing routes
in from a somewhat external source,
the ASBR can also do summarization. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
the ASBR can also do summarization.
But that's it.
So if we wanted to summarize-- if this was like area 1,
and we want to summarize between R5 and R7, not so good,
because the link state advertisements
and the link state database has to be consistent.
We might be able to trick a router into like not believing
something in the link state database,
but as far as summarizing, it's got
to be between areas or at the ASBR
as we're bringing routes in.
For other routing protocols, like RIP, EIGRP,
we can do those at interfaces. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
we can do those at interfaces.
Though if we were running all RIP--
not too likely we're running all RIP here.
But if we were running all EIGRP,
we could specify that, hey, here at R3, what we could do
is we could specify on this interface and this interface
as we advertise routes.
We could summarize the 10.1.35 network, and the 10.1.57
network, and the 10.1.7 network.
We could summarize those at the interfaces
as we advertise towards R4 and up to R1.
So in RIP and EIGRP, it's at the interfaces on the router WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So in RIP and EIGRP, it's at the interfaces on the router
where we can actually advertise the summary
and suppress the more detailed routes.
If we're running BGP, we certainly
have some fantastic options with setting up
aggregates or summaries of addresses with BGP
as we shoot information or advertise
routes who are BGP peers.
So we're going to have Knox.
He'll cover the BGP summarization
in those specific videos on BGP.
However, in OSPF and with the ABRs and the ASBRs, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
However, in OSPF and with the ABRs and the ASBRs,
in the OSPF specific videos regarding
those protocols in this course, I've covered summarization.
I'm giving you some examples there.
I've also touched on some summarization in EIGRP
in those videos.
However, what I want to do in these videos
is just give you an overview of some of the options,
and I also want to-- in this video instead of labs,
I also want to give you an opportunity
to practice with summarization in something other
than traditional EIGRP, including named EIGRP.
So one little caveat. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So one little caveat.
I've got a whole separate set of videos in this series regarding
named EIGRP.
And what we're going to do in this set
is I'd like to give you some practice in getting introduced
to it, if you haven't seen that other part yet,
and also how to do summarization with EIGRP, whether or not
it's named EIGRP or the traditional flavor.
And the other thing I wanted to point out,
as far as summarizing, we don't want to summarize too much.
For example, what would be too much?
Well, R3, as an example here, if R3 knows about these 10.1.x WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Well, R3, as an example here, if R3 knows about these 10.1.x
networks down here--
they're actually slash 24's-- and he's going to summarize,
it would be a bad idea if he summarized and said, hey,
I'm going to summarize that to an 8-bit boundary.
10 anything is reachable.
Because if he advertises the 10, and then over here an R4,
which has to 10.2 networks--
I'll put an X there--
slash 24.
If he advertises a summary and says, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
If he advertises a summary and says,
hey, 10 anything, if he advertises them as a slash 8,
then you have two routers both advertising a 10 network.
And trust me.
They're not all in the right places.
I mean, 10.1 is over here explicitly.
10.2 is over here explicitly.
So we don't need two routers both saying 10 anything,
come my way, because then we're going
to have problems with routing.
So one of the key elements is make sure
that when you're doing a summarization,
you're summarizing routes that you actually have
or have reachability to.
The other thing that happens, too,
with summarization when we do manual summarization WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
with summarization when we do manual summarization
with EIGRP, it's going to create a discard route.
And it's actually pretty cool.
We'll get a chance to see this in the lab.
So if we trained R3 and we trained it to do a 10.1.X.X
with a 16-bit mask as a summary, as it advertised R1 and over
here to R4.
When we do that, it's going to create a route in the routing
table for the 10.1.0.0/16 that goes to the bit bucket,
which is spelled Null0. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
which is spelled Null0.
And the reason for that is that if R3
says, hey, I can get to 10.1 anything,
or here's this route, if packets are forwarded
in that direction, and then based on the destination
address, R3 doesn't really have a more specific correct route,
we don't want it to go ahead and use its default route, right?
So by setting up--
when we do the summary, by having it automatically create
a route that goes to Null0, if there's
packets that don't match any other more WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
packets that don't match any other more
specific routes in the routing table, it just drops it.
And that's going to help prevent a loop.
We'll have a chance to see that when we lab it up as well.
Now there's one more point I'd like to talk about.
And that is auto summarization, which
has been turned off as a default for many, many years
with RIP and EIGRP.
But in the next video and lab, I'd
like to talk with you about what that issue is,
give you a chance to see it first hand,
and then realize, oh, yeah, yeah,
that's a bad idea, that auto summarization.
So I'll see you for that in the next video.
Meanwhile, I hope this has been informative for you. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Meanwhile, I hope this has been informative for you.
And I'd like to thank you for viewing.