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[AUDIO LOGO]

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So now that we've looked at
the different type of LSAs

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in more detail, now it's time
to jump onto the command line,

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take a look at these
LSAs in the database

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so we can see what
they actually contain,

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and take a look at
the different fields,

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and what they represent
in our OSPF environment.

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So let's start by
looking at our diagram.

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So remember what our
topology looks like

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and what our different
area types are.

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And then we'll jump
in to the command line

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and take a look
at that database.

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So for this demonstration,
we'll again,

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be using OSPF topology 2.

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And just some things
to keep in mind

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as we're going
through this, area 200

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is configured as an NSSA.

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We have router 6
acting as the ABR

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between area 0 and area 200.

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We have router 1
acting as an ABR,

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as well as router 3 for
area 100 going into area 0.

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And we have router 2 who's an
ASBR, redistributing the EIGRP

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routes into area 100.

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Also as a note, router 10
has a loopback interface

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that is also being redistributed
into OSPF in the NSSA.

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This topology is going
to allow us to look

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at all of our LSA types.

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We'll see 1 and 2
looking in area 0.

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We'll see type 3 LSAs coming
from areas 200 and 100.

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We'll also see some type 5
LSAs, along with type 4 LSAs

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coming for the routes from
router 9 and from Router 10.

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Then we'll take a
look at our type 7

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LSA in our NSSA area, area 200.

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So let's jump in and start
looking at the different LSAs.

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And we'll be looking
primarily at router 7.

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But, of course, we'll have
to jump up to router 6

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to look at our type 7.

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But let's begin on router 7.

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So let's start by just
looking at the routing table.

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Just do a show ip route ospf.

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And what we see here
is we do, in fact,

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have a combination of inter-area
routes, intra-area routes,

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and external routes.

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Another good command to keep an
eye on is show ip ospf route.

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This actually shows
the OSPF routing table.

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These are the routes that
OSPF has chosen as best,

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and is trying to put
into the routing table.

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We can actually see
here the routes that

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have been chosen as
best, and it's trying

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to put into the routing table.

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Let's talk just for
a moment about where

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these different components fall
into the OSPF decision process.

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The first thing is the
link state database

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with its entries.

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This, of course,
is what we're going

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to be looking at mostly
in this demonstration.

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The best routes from
the link state database

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are then put into the OSPF RIB.

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This is the O-S-P-F RIB.

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And that's what this command
we just looked at showed us.

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This is what we see with
the show ip ospf route.

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The routes that are
actually marked for entry

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into the routing table then
get put into the global RIB.

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This, of course, is what we
see with the show ip route.

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And not that it's incredibly
important to this discussion.

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But just to wrap
this up, of course,

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all of the entries
in the global RIB

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then get installed into the FIB,
or the Forwarding Information

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Base for CEF or Cisco
Express Forwarding.

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So ultimately, this is the
table used for the actual packet

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forwarding.

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So again, just as a review.

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If we do a show ip
route, we see this table.

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If we do a show ip ospf route,
that's when we see this table.

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That's the last
command we just did.

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And, of course, for the
rest of this discussion,

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we're going to be
looking at the database.

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So when we do a show
ip ospf database,

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we'll be looking at the
link state database.

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And just for completeness, if
you want to look at the FIB,

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on most platforms, it
would just be show ip cef.

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But let's go ahead
and take a look now

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in more detail at
the actual database.

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So let's just start with
the show ip ospf database.

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This just gives us
a summary of all

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of the different LSA types that
are currently in our database.

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We'll be looking at
these in more detail.

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But this is just
like a summarization.

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And if you actually
just want a count,

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there's also other options
here for filtering this.

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One of them is database summary.

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So it's sort of funny because
the command can actually be

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show ip ospf database database.

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And what this does
is just show us

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a counter of literally
how many of each

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type are in the OSPF database.

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What we're going to do,
though, is focus more

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on the individual types.

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So let's start by taking a look
at the type LSA or the router

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LSAs.

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So we'll take database off of
here, and we will say router.

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Now this first
entry happens to be

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the entry coming from router 1.

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The first thing we
see is the LS age.

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The LS age here is how long
this has been in the database.

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We also have some options.

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We have no TOS capability.

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TOS is type of service.

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This is simply not
supported on Cisco routers.

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So this will pretty much always
just say no TOS capability.

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And then we also see DC here,
which is demand circuit.

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It just means that
this router is

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capable of doing
demand circuits.

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We see the LS type
is router links.

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That make sense, because that's
what we asked to look at.

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We see the link state ID,
which is the router ID.

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And the advertising router
is also the router ID.

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These are going to be
the same on type 1 LSAs.

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They'll be different
on other types of LSAs.

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We also see the
sequence number, which

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we use to ensure that the
database is up to date.

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The checksum, of course,
for error correction,

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the length in bytes.

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And we also see that router 1
is announcing itself as an ABR

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into the environment.

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Then we see that
it has four links.

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And then it starts
breaking them down for us.

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So we have one link that's
connected to a stub network.

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That stub network is 10.1.1.1
with a mask of a /32.

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Now just based on our
topology and our knowledge,

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we happen to know that that's
its loopback interface.

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Our second link here is
connected to another router.

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It's a point-to-point link.

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And that's connected
to router 3.

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We also see its IP
address on that interface.

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If we scroll down, we see
that it has another connection

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to a stub network.

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Notice that it's also listing
that as the link 2 router 3.

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These point-to-point
links are listed

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both with a topology entry, as
well as a network advertisement

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being a stub network.

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Then we have the
transit network,

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which is the multi-access
network between routers 1, 6,

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and 7.

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This is listed as
the transit network.

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We see who the DR is.

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In this case, the
DR is actually .7,

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which makes sense because
it's the highest IP address.

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And our interface on that is .1.

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Now as we can see,
we have other entries

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here from other routers,
here starting with router 3.

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But we're not here to look
at the whole database.

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We just want to look
at the different LSAs.

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So next, since we know we
have this transit network,

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let's take a look
at our type 2's.

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So we'll take off router,
and we'll put in network.

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So here's that type 2 LSA.

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Notice that it's coming
from the DR. Notice

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the link state ID is
the address of the DR,

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and it even tells us that.

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Also we see that the
advertising router

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is in fact router 7's router
ID, which make sense since he's

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the DR.

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And then notice down here it
lists the subnet mask in use

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on that network.

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So the network mask, along
with the link state ID would

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actually tell us what the
network is, 50.0.167.0/24.

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Those two pieces of information
together define the network.

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And then, of course,
here at the very bottom,

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it lists all of the router
IDs attached to that segment.

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Notice that the other fields
that we didn't mention

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are just the same as
they are in a type 1.

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Next up would be the type 3's.

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These are called
summary LSAs, of course.

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The first thing
to notice here is

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that the type 3 LSA has this new
option on it that says upward.

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This is referred to as
the OSPF downward bit.

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And I know that seems
odd since it says upward.

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But the thing is
the option being

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set to upward simply as a way of
saying that the downward bit is

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not set.

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So we generally call
this the downward bit.

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And we'll talk about this
more when we get into MPLS.

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This is for MPLS
loop prevention when

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we're dealing with duplicate
PES and things like that.

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So we'll get more
into this later.

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But just for now, be
aware that this is where

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it's carried in the type 3 LSA.

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And if we're not dealing
with MPLS and VRFs,

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then this is going
to be set to upward,

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meaning again the downward
bit flag is not set.

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So next, we see
the link state ID,

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which in these first
two examples here,

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notice that they're
both 10.2.2.2.

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That's actually router
2's loopback interface,

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which is over in area 100.

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Notice that we're learning this
from two different advertising

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routers because we have
two different ABRs--

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10.1.1.1 and 10.3.3.3.

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The only other
thing to note here

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is the network mask is carried
down here at the bottom.

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So again, if we apply
the network mask

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with the link state ID, which
is the actual network being

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advertised, this tells
us the actual network.

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If we scroll down to something
that's a network rather than

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a loopback address.

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So for example, these entries.

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We have an entry here for
the network 50.2.61.0.

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Now we can see
that that's a /24.

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So this is telling
us that, that network

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is available through router
6, which of course, is also

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an ABR.

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Next up, let's take a
look at our type 5's.

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So these are going
to be external.

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And for now, we're just
going to focus here

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on router 9's loopback.

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It happens to be
our first entry.

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So first thing to
note is it again,

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has that upward bit or the
downward bit that's not set.

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So listing it as upward.

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And then notice that once
again, just like a type 3,

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the link state ID is the actual
network being advertised.

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So it's 10.9.9.9.

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But here's the important part.

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The advertising
router is 10.2.2.2.

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That is a router
not in our area.

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We would have no idea how to get
to 10.2.2.2, because we do not

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have a type 1 LSA for it.

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We'll demonstrate
that in just a moment.

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But notice we also have
the network mask here.

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And external type 5 LSAs do
carry some extra information

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here.

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They have the metric
type, which can either

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be a type 1 or a type 2.

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We'll cover that in more
detail in a future skill.

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We also have a metric listed
here, the forwarding address,

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which we will also
cover in more detail,

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as well as any
external route tag

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that may be set on this route.

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Now again, the problem
with getting to 10.2.2.2

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is if we do our show
ip ospf database again,

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and this time we
say router 10.2.2.2,

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notice that there's no entry.

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00:12:27,850 --> 00:12:30,610
Again, 10.2.2.2 is
in a different area.

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00:12:30,610 --> 00:12:31,930
It's over in area 100.

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00:12:31,930 --> 00:12:34,060
And we're currently in area 0.

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00:12:34,060 --> 00:12:37,360
This router, router
7 would have no idea

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00:12:37,360 --> 00:12:39,730
how to get to this
advertising router.

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00:12:39,730 --> 00:12:43,640
And this is exactly what the
type 4's are going to give us.

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00:12:43,640 --> 00:12:44,980
Let's take a look.

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It's actually ASBR summary.

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00:12:47,020 --> 00:12:48,610
I usually just type ASBR.

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00:12:48,610 --> 00:12:51,050
But there's the whole
command for you.

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00:12:51,050 --> 00:12:54,760
And notice exactly what
this is telling me.

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00:12:54,760 --> 00:12:57,580
Notice what the
link state ID is.

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00:12:57,580 --> 00:13:00,310
And we don't have to go into a
whole lot of detail on these.

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00:13:00,310 --> 00:13:04,750
Notice that they're almost
identical to type 3's

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00:13:04,750 --> 00:13:06,920
that we just talked
about a moment ago.

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00:13:06,920 --> 00:13:10,090
The only thing that makes
these different from a type 3

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00:13:10,090 --> 00:13:12,820
is what's being advertised.

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00:13:12,820 --> 00:13:14,590
The link state ID.

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00:13:14,590 --> 00:13:16,120
And it even tells
you in parentheses

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00:13:16,120 --> 00:13:17,860
afterwards what it is.

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00:13:17,860 --> 00:13:20,890
It's the AS boundary
router address.

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00:13:20,890 --> 00:13:26,140
Specifically, it is the
router ID of the ASBR.

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00:13:26,140 --> 00:13:28,750
And notice that just
like with the type 3's,

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00:13:28,750 --> 00:13:32,770
we're getting this information
from both of our ABRs--

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00:13:32,770 --> 00:13:36,400
10.1.1.1 and 10.3.3.3.

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00:13:36,400 --> 00:13:39,550
So finally, let's
look at type 7's.

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00:13:39,550 --> 00:13:41,590
But as I mentioned
before, we can't exactly

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00:13:41,590 --> 00:13:44,920
look at them here because
if we say NSSA here,

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we're going to have no entries.

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00:13:47,050 --> 00:13:52,990
Remember that the type 7 only
lives inside of the NSSA.

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00:13:52,990 --> 00:13:56,110
Router 7 here is
not in the NSSA.

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00:13:56,110 --> 00:13:57,670
So we're going to
have to jump over

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00:13:57,670 --> 00:13:59,740
to a router that is in there.

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00:13:59,740 --> 00:14:01,270
We'll just use router 6.

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00:14:01,270 --> 00:14:04,810
So on router 6, we'll do
our show ip ospf database.

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00:14:04,810 --> 00:14:07,150
And we'll do the NSSA here.

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00:14:07,150 --> 00:14:10,990
And we'll see that now we have
a type 7 for that loopback

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00:14:10,990 --> 00:14:16,910
interface on router 10, which
happens to be 100.10.10.0.

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00:14:16,910 --> 00:14:21,280
And as we can see by the
network mask here, it's a /24.

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00:14:21,280 --> 00:14:23,210
The advertising
router, of course,

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00:14:23,210 --> 00:14:25,390
is router 10's router ID.

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00:14:25,390 --> 00:14:30,550
Notice that this is almost
identical to a type 5 LSA.

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00:14:30,550 --> 00:14:32,800
And it doesn't really
need to be any different,

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00:14:32,800 --> 00:14:34,420
because we're just
using the type

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00:14:34,420 --> 00:14:37,660
7 to get this through the NSSA.

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00:14:37,660 --> 00:14:41,230
We'll be covering this in
more detail in a future skill

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00:14:41,230 --> 00:14:45,530
when we cover OSPF area
types in greater detail.

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00:14:45,530 --> 00:14:47,710
But all we really need
to see for right now

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00:14:47,710 --> 00:14:52,600
is the fundamental difference
on this LSA from a type 5,

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00:14:52,600 --> 00:14:57,550
is this option here that
says type 7/5 translation.

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00:14:57,550 --> 00:15:02,080
It's basically the originator,
in this case router 10,

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00:15:02,080 --> 00:15:06,670
asking our ABR, in
this case, router 6,

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00:15:06,670 --> 00:15:10,960
to translate this
into a type 5 LSA.

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00:15:10,960 --> 00:15:15,970
And in fact, if we say
show ip ospf external

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00:15:15,970 --> 00:15:18,610
and filter it by
self originated,

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00:15:18,610 --> 00:15:21,440
notice we are, in
fact, translating it.

301
00:15:21,440 --> 00:15:22,610
There it is.

302
00:15:22,610 --> 00:15:27,550
This is us generating the type
5 on behalf of the type 7.

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00:15:27,550 --> 00:15:31,060
We are doing the translation.

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00:15:31,060 --> 00:15:33,970
If we do a show
ip ospf, and if we

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00:15:33,970 --> 00:15:36,440
look at our information
for area 200,

306
00:15:36,440 --> 00:15:41,770
notice it even says perform
type 7 to 5 LSA translation.

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00:15:41,770 --> 00:15:44,240
And we can see that router 6 is.

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00:15:44,240 --> 00:15:47,950
Again, we'll be covering this in
more detail in a future skill.

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00:15:47,950 --> 00:15:51,140
But I at least wanted you
to see the type 7's for now.

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00:15:51,140 --> 00:15:55,170
So you can get an idea
of how these work.

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00:15:55,170 --> 00:15:58,410
In this video, we jumped
into the command line,

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00:15:58,410 --> 00:16:02,790
and really got a detailed look
at each of these LSA types,

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00:16:02,790 --> 00:16:05,760
what they look like, what
information they contain.

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00:16:05,760 --> 00:16:10,470
We even got to see how
our ABR between an NSSA

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00:16:10,470 --> 00:16:13,740
and a normal area,
in our case, area 0,

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00:16:13,740 --> 00:16:20,430
how that ABR is translating the
LSA from a type 7 to a type 5.

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00:16:20,430 --> 00:16:22,560
I hope this has been
informative for you,

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00:16:22,560 --> 00:16:25,460
and I'd like to thank
you for viewing.

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00:16:25,460 --> 00:16:29,000