This is one of multiple OSPF videos.
I was asked to explain OSPF multiple areas and this is one of multiple videos helping explain how OSPF
works when you have multiple areas configured.
Rather five is another area border.
Rather it exists between area zero and area two.
So bypass the initial configuration dialog.
And I'll configure this as right.
A five interface gigabit.
Zero zero no shut IP address.
Ten 142.
Slash 24 mosque.
So that was the IP address configured on gigabit zero zero on interface gigabit zero one IP address
ten 151.
Slash 24 musk and I'll create a loopback of quadruple five.
So do show.
IP interface brief.
IP addresses are configured on the various interfaces.
I forgot a no shut gigabit to zero one.
So there we go.
On this Friday we are going to configure OSPF, but what we're going to do now is make sure that we
configure and I'll do it slightly differently now.
We'll configure gigabit zero zero in Area zero.
So we're saying this interface gigabit is zero zero, which has an IP address of ten 142 is going to
be put into area zero because of the mask used here.
It's an inverse mask.
I'll also put the loopback of the router into area zero and then I'll configure.
Gigabit.
Is there one in area two.
So show run section OSPF.
That's the configuration of OSPF on the router.
Show IP OSPF interface brief.
At the moment we only have OSPF enabled on one interface and that's because I made some mistakes.
So let's redo that.
No network.
Four, four, four, four.
Should be network.
Five, five, five, five.
Show ip ospf.
Interface brief we've got OSPF running on the loopback and gigabit is zero zero so show IP interface
brief ten 151 is configured on gigabit is zero one.
Let's see what I did wrong in OSPF.
I put this as a zero.
Rather than using the right mosque.
So no network ten 150.
This should have been done.
Like this.
So show IP OSPF interface brief.
That looks better.
OSPF is configured on three interfaces.
Show IP route.
We are learning in area routes, in area routes and external routes.
And rather five should be able to ping rotor one, which it can.
And we can see the output on router one.
Okay.
So the lost router to configure is router six.
This is an internal router.
All interfaces on this router belong to area two.
So bypass the initial configuration dialog and I'll configure the router.
So it should be right of six interface gigabit zero zero no shut IP address ten 152.
So that's the IP address on gigabit zero zero.
Interface loopback zero.
IP address quadruple six.
As follows.
Router ospf one network and I'll just do it this way to keep it simple.
All interfaces in this example belong to area two.
So show IP OSPF interface brief.
Show IP OSPF interface brief shows us that OSPF is running on both gigabits or zero and the loopback
show IP OSPF neighbor shows us our neighbor relationship two out of five show IP route shows us our
routing table.
Now here we don't see any intra area routes because this Ethernet interface and the loopback of the
local router are seen as directly connected rather than being advertised by a writing protocol.
So we see inter area roots and quite a few of them as well as external routes.
Row two six should be able to ping rather one, which it can and we can see the debugger and router
one.
So show IP OSPF database.
Notice that on router six this command shows us only area two because the route is only configured in
area two.
It sees that router six and router five are configured in area two.
It sees that router five is the designated router on the Ethernet segment in area two, it sees a range
of losses.
These are into area routes, LSA Type three.
It sees a type for LSA, which is a summary SBR LSA, and it sees external routes.
So there you have an example of many LSA types that you get in OSPF LSA type one rather less LSA Type
two network link Alice's.
Top three summary lists, type for April essays and top five external essays.
Let's have a look at Root of five, which has interfaces in multiple areas.
So show IP OSPF database, you'll notice it displays information for area zero as well as for area to.
So on Area zero, we have three routers and Area zero, we have two designated routers in Area zero.
So to net the link states, these are summary lists or routes coming from other OSPF areas.
There is one autonomous system.
Border writer Alyssa.
Then we see similar information for Area two and right at the end we see the external losses or less
top five.
That was an example of how to configure multi area OSPF.
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