We've been told once again in this network that rather one is not able to ping the loopback of router
four.
So let's check what's happening in the network show IP protocols.
We can see that rather one is running a routing protocol.
In this case it's OSPF with process id one show IP ospf neighbor.
Rather one has an OSPF neighbor relationship to router to the relationship is full, so that's good.
Neighbor IP addresses this local interfaces this show IP router shows us that we are learning OSPF routes.
So that is good.
Can we ping the loopback of router two?
Yes, we can.
Can we ping ten 1 to 1?
Yes, we can.
So we can ping this address.
Can we ping ten?
One, two, two.
No, we can't.
So we can't ping this IP address in our network.
We are also not learning about the loopback of router four.
So if we did do a trace, the traffic would simply be dropped by the local router, rather one because
it doesn't know where to send the traffic.
So again, show IP route shows us that we are only learning about this network and this network we can
ping up to here, but we can't ping.
Router three.
So let's have a look at rather to show ip ospf neighbor.
Now here we've only got one neighbor relationship.
We've got a neighbor relationship to router one router one has this loopback address configured.
Router two has a neighbor relationship on gigabit or zero zero.
Slash is zero.
Two Errata with us errata ID and the IP address show IP route.
We are learning about the loopback of router one.
Router two can ping the loopback of router one but is not forming a neighbor.
Relationships with router three.
Has rotted to got OSPF configured and enabled on gigabit 001.
Show IP OSPF interface will show us that and the answer is yes.
OSPF is enabled on this interface in area zero.
Can this rather ping rather three?
Yes, it can.
So we have IP connectivity between router two and router three, but rather two is not forming a neighbor
relationship with a router three even though OSPF is enabled on this network.
In other words, on this interface.
So why is no neighbor relationship formed to router three?
So in rota three show IP protocols.
Can you see the problem based on the output?
Pause the video now if you need more time.
Okay.
So have a look at the networks.
Can you see the problem?
Here's another hint to show IP OSPF interface.
Notice OSPF is only enabled on the loopback interface and gigabit is zero zero.
OSPF is not enabled on gigabit or 0/1 show IP protocols.
Why is it not running on this interface?
Have a look at these network commands and if we do a show run pipe begin OSPF and I'll scroll up here.
There's our router OSPF configuration.
Notice these network commands.
Give us a that result.
Why is OSPF not running under this interface?
That's because this inverse mask is looking for ten.
Dot one.
Dot zero anything OSPF is only going to be enabled on network ten one zero ten 130 and 3.323.3.
But this network isn't configured on the router.
Show IP Interface Brief.
We have this IP address ten 13.1 ten 12.2 and 32323.3.
We don't have network 1.1.0.
So this command is wrong.
So concerti rather ospf one no network.
Ten .1.0.0.
Area zero.
That should be Network ten .1.3.0.
And now that I've enabled that command notice neighbor relationships are being reset to router for.
And that's actually incorrect.
I should use that command network 10.1 or 2.0.
And notice now we see a neighbor relationship to router two.
So just to confirm, show run.
Show ip ospf neighbor.
We have a neighbor relationship.
This command is incorrect.
So let me redo that.
That should be
network ten 130.
Area two.
So be careful that you don't introduce additional problems into your network when making changes.
Show IP OSPF neighbor that looks better.
We have two neighbor relationships.
Show IP route.
Route.
Look better.
This router can ping the loopback of router four.
Right.
A two now has a neighbor relationship to router three to show ip ospf neighbor.
The neighbor relationship is showing.
Show ip route shows us that we've got a route to the loopback of router three and we can ping the loopback
of router three.
But we're not learning about network four.
Let's check that on router three.
The network is displayed, so I'm going to clear the OSPF process to force packet tracer to recalculate.
Sometimes if you make a mistake like I did there.
Packet tracer causes problems and you have to re start the OSPF process.
So show IP rot.
We still not learning about that neighbor relationship.
Let's check if I introduced another problem.
Otherwise I'll reset routers again on router three.
But that looks good.
We can ping the loopback of right of one and the loopback of router for.
And rather too, we're not seeing Network four on router one.
We're not seeing the loopback over out of four, but we can ping this IP address on router four.
So what I'll do is reset router four.
Clear ip ospf process.
Let's see if that sorts out the problem.
Show IP OSPF database.
That looks good.
We've got two as an area to show IP route.
We are learning a bunch of routes and we can ping the loopback of router one on router one.
We still not learning about the loopback of router four.
So what I'll do on router four is re add that network sometimes in packet trace if you make a mistake
or like I made.
It can cause problems.
So what I'll simply do actually is remove OSPF and then add it back again and enable OSPF on all interfaces.
Show IP route.
We just need to give that a bit of time and hopefully the neighbor relationship will be formed.
That looks better.