So we've been told once again that rather one is not able to ping the loopback of router four and that's
what we're seeing in the lab.
So on router one show IP route, we don't have a route to network four in the routing table, but we
are learning routes through OSPF.
So as an example, we can ping the loopback of router to show OSPF neighbor shows us that we have a
OSPF relationship to router two.
And rather to.
We can confirm that rather too has this IP address configured.
On loopback is zero and that's the IP address.
That router one can ping, but rather one doesn't see network four in its routing table and neither
does router to write a two is learning about the loopback of right one.
So router two can ping the loopback of router one, but it doesn't look like it's learning about the
loopback of router three, which is 3.3.3.3.
And it's also not a learning about the loopback of router four.
So show IP protocols once again shows us that we running OSPF with process ID one.
We have two normal areas configured, so a number of areas in this routers two.
There are two normal areas, zero stub and zero not so stubby areas.
The router knows about rather one and itself again on router one.
The loopback.
He's configured as follows.
But the Rada doesn't know about Rada three or out of four.
Is OSPF enabled on this interface?
So show IP OSPF interface OSPF is enabled on the loopback interface of the router.
It's enabled on gigabit 001.
In other words, it is enabled on this interface and it's also enabled on gigabit 000.
So OSPF is configured on this interface.
Can we ping root of three?
Yes, we can.
So we have IP connectivity to router three, but we don't have an OSPF relationship to router three.
Even though OSPF is enabled on this network.
So let's have a look at router three and see if there's a problem on router three.
He has brought a three show IP protocols.
OSPF is enabled on this router.
Number of areas configured on the shroud is one.
There's one normal area configured on the Cerrado.
So IP OSPF interface.
So let's have a look at this output and compare it to the output on rather two.
Can you see a problem here?
Based on this output, you should be able to see a problem.
What's the problem here?
Pause the video if you need to at this point.
Okay.
So have a look at the output on gigabit or zero one, which is this interface versus gigabit 001, the
output on this interface.
Notice the area configured on 10.1 or 2.1 is area zero.
Whereas on this site it's area two, OSPF requires that neighboring routers be in the same area.
So show run shows us that this interface has been configured in area two.
This interface needs to be configured in Area zero to match router two.
It's a requirement in OSPF that all areas be connected to area zero.
The area configured on this side is area one.
So router two is an area border router or ABR with this interface in area zero and this interface in
Area one.
That means that router three should have this interface gigabit or zero zero configured in another area
such as area two.
But this interface should be configured in area zero.
So conf t interface gigabit zero one ip ospf one, area zero show run.
That interface is now configured in area zero.
And notice what we see on the side.
Router two has formed a neighbor relationship to router three on gigabit 001.
On this side, however, we don't see any output.
Show IP OSPF neighbor shows us that we have two full relationships one to router two and one to write
a four.
So that looks good.
But why are we not seeing output on the screen?
And here's your answer.
We want to enable logging to the console.
Be careful in the exam.
You may not be able to do that.
But logging to the console will show us when a neighbor relationship goes down and when it comes up
again.
So as an example, notice here we can see that the router has been configured from the console by the
console.
Again, Control Z or Control Z shows us that when logging is disabled, you won't see that output and
you won't see messages on the screen such as this.
So make sure that logging is enabled.
Okay.
So can router three ping the loopback of router four?
Looks like it can't.
So we need to check what the problem is on the side of the network.
Show IP route.
Router three is learning rots and can ping the loopback of rotor.
One is an example and keeping the loopback of router two but can't ping the loopback of router four.
Can it ping a router for?
Yes, it can show ip ospf interface.
Thus interface gigabit is zero zero is enabled in OSPF in area two.
The loopback is enabled in area two and gigabit is zero one.
So that looks good.
Let's check what's happening on right for.