- [Instructor] In this video we want to compare
a couple of OSPF network types
and by the way, the encore blueprint wants us to know
about two specific network types,
the broadcast and the point-to-point network type.
So we're going to take a look at some of their characteristics.
There are some other network types,
but you might get into those if you're dealing with
a frame relay or an ATM network
and we don't really see those that much these days,
so we're really focusing on
more relevant network types here.
First consider the broadcast network type.
With a broadcast network, we're saying that
everybody is on some sort of an ethernet network.
We all have an ethernet interface connected
to the same subnet, the same IP address space,
and we're going to be able to send a broadcast
and it would reach every router on this broadcast network.
Now we're not going to use broadcast,
but that's what we would happen if we did send a broadcast.
And the broadcast network type is the default for OSPF
on any type of ethernet interface
and because we could have multiple routers
connecting to the same subnet
and we could get into that scalability issue we talked about
where we had the DR and BDR,
it might be a good idea to elect a DR and a BDR
on a broadcast network type.
So that's what happens.
We'll elect a DR and BDR on a broadcast network type.
And again, a requirement is all routers have to have
an interface on the same subnet.
The other network type we have
is a point-to-point network type
where we have a couple of routers
directly connected to one another.
And with a point-to-point network,
we are going to be saying that we're on
a non-frame relay connection
because our frame relay connection could be
one point going to multiple other points.
It could be a point-to-multipoint connection.
So a point-to-point network type,
that's going to be the default OSPF network type
for a serial interface that's not configured
for frame relay.
So if we have a serial interface configured for
HSRP or PPP, the point-to-point protocol,
yeah by default it's going to be
a point-to-point OSPF network type.
And because there's only two routers on this link,
there's really no need for a DR or a BDR.
We're not going to have a scalability issue
because there's only two routers on this link.
So a DR and BDR, they are not elected
on a point-to-point network type,
but each router does have an interface, of course,
on the same subnet.
And that's a quick comparison between
the OSPF broadcast and point-to-point network types.