Okay.
So in Wireshark we see a whole bunch of messages.
So he has ARP, he has OSPF, CDP, a bunch of protocols being sent on the network.
But I'm going to filter for OSPF.
We've got to rotters.
This is rather to this is rather one.
So let's have a look at rather 1/1.
So rather one is the right on the left hand side frame is IP version four from this MAC address, sending
a multicast to the well known multicast for OSPF, the layer three protocol referenced here is IP version
four.
So at least three we see IP version four.
Source IP address.
Destination IP address.
Protocol number is 89.
That looks good.
That means ospf down to the bottom here.
So let's have a look at OSPF.
Look at the header.
The version is open version two it's a hello packet router IDs this it's got a backbone area.
Password is set to this.
So that all looks good.
So let's have a look at rather to see if we can see a difference.
That all looks great thus far, so we can't see a problem there.
Let's have a look at the hello packet and see if you can see a problem right away.
What's the problem here?
Can you see the issue?
Notice this mask is different now for OSPF routers to form neighbor relationships, they have to use
the same subnet mask.
This IP address on this side is set to ten 123251.
On this side it's set to ten one, three, two, five, two.
But notice the network masks are different.
If the network mask is different, they are not going to form a neighbor relationship, which means
they're not going to exchange routes, which means it's not going to work.
So what I'll do here.
Actually start a new Wireshark capture so that you can see what it looks like once things are fixed.
So OSPF at the moment we are seeing the problem from the original Wireshark capture.
So in the header.
Let's have a look at the hello packet.
Notice the masks are different.
Different masks over here.
So what I'll do is have a look at these routers.
So there's router one.
And he has rather to.
Okay.
So rather one it to boot it up show ip ospf neighbor notice no neighbor relationship show ip ospf neighbor
no neighbor relationship show ip ospf interface brief.
We can see that OSPF is now running on three interfaces a loopback plus two physical interfaces show
ip ospf interface brief same thing on the side.
So in the OSPF captures, you'll notice that the.
Loopback address is used as the OSPF router ID, even though the IP address that's sending out the multicast
is the physical IP address on the interfaces.
So notice router one has this loopback router as this loopback.
That's fine from an OSPF point of view, but if we have a look at the configuration and let's do it
this way, show interface or IP interface gigabit is zero one on this side and on this side, show IP
interface gigabit is zero zero.
Notice the subnet masks are different.
Slash 26.
Slash 24.
Show run interface gigabit zero zero.
Slash 24 on the side show run interface gigabit zero one slash 26.
So in this side interface gigabit zero one IP address ten
132512552452550.
Hopefully once that happens.
If there are no other problems, the neighbor relationships should be formed.
And there you go.
Notice loading is set to fall, so show IP SPF neighbour neighbour relationship is up.
Show ip ospf neighbor neighbors are up.
Just make this a bit bigger.
So neighbor relationships are formed between the two writers show IP route.
We see OSPF routes in the routing table.
That looks good.
So if we go back to Windows, they should hopefully be able to ping each other, which they can.
The two Windows PCs.
PC one and PC two can now ping one another.
Remember in OSPF, the subnet masks have to be the same for the routers to form neighbor relationships.
The subnet masks are different.
They won't form a neighbor relationship.
Hope you enjoying these troubleshooting videos.
It's important that you know why.
A shock.
It's important that you know your protocols.
I like to say that the best way to learn is to troubleshoot.
And Wireshark is a great way to actually learn what's going on.
Not in theory, but in practice.
This is like running a real physical network and capturing the traffic.
You can actually see what's going on.