So now with that quickly reviewed,
let's move on and talk about the link state update packet type.
This packet type is used by a device to send back the LSA
information that was requested with the LSR packet type.
It contains two different main fields.
The number of LSAs that are being sent in the update and the LSAs themselves,
in this case the complete LSAs.
Since there are so many different types of LSA,
they will be covered in a bit more detail in the next module,
but for now let's move back to the capture and show an example of this again.
So again let's move back to the same capture.
This was Core 1 requesting all these different LSAs from Core 2,
and then this is Core 2 with an update packet,
and it requested several.
(Typing) Now if we remember from this previous message,
the request was for all of these so the first one was link state
id 2.2 .2 .2 and advertising router 2.2 .2 .2.
Okay, so if I look at this update packet,
this is the full LSA, not just that triplet information,
but the router LSA, the link state id is 2.2 .2 .2,
the advertising router is 2.2 .2 .2,
and this is all the information that's contained within that LSA.
And as can be seen here,
this is where we really get into the meat of reachability
information that goes between these different devices.
Up until this point we're just talking about what entries you have,
but in this case now we're starting to get into what networks are going
between point A and point B throughout the network,
and again we're going to talk about what the specific
link types are in the next module,
but for now just know that like this is one example of a router
LSA that contains information about the reachability of certain
IP networks in the OSPF domain, and in here,
we can see in this case it's discussing who the DR is on a
specific link and where to find other information.
We show these later ones, these all have,
I mean this one only has one,
and then we can also show like here is the network 10.10
.10 .2 with a 252 so this is actually the network that
goes between Core 1 and Core 2,
which has a 255.255 .255 .252 network mask and the
two routers that are on there, Core 1 and Core 2.
So this is actually just advertising the network between
Core 1 and Core 2 on that direct link.
And then all the rest of these,
since I have OSPF neighborships established between all the
devices and the topology that we showed,
this is just sending all that information that is known
currently by Core 2 and sending it to Core 1.
So let's move back for an additional slide and we'll talk real briefly about the next packet type and move back.