Okay.
So let's have a look at the Wireshark capture.
Here's the IP address of one of the routers.
Ten one, three, two, five, one.
And that route is sending a multicast to 224005.
He has the other router ten 132 sending a multicast to the same destination IP address.
Again.
I'm going to go a little bit more in detail here.
Hopefully you'll learn something.
Source Mac addresses this.
That's the destination Mac address for OSPF at layer two.
So this is the layer two frame.
So the vendor portion is 01005e host portion starts with a zero followed by 23 bits taken from the IP
address.
So if you look at these 24 bits first, but are set to zero, then remaining 23 bits is the actual IP
address.
In this case, it works out to be the same.
So 000005.
That is the multicast mac address for the IP version for OSPF multicast address.
Okay.
Type at layer two is zero 800.
That means IP version for so layer three, we see IP version four, source IP address, destination
IP address.
We see information such as DHCP, once again, very important traffic here clause select a six, one
of the highest types of traffic from a quality of service point of view, more important than voice
of IP video or any other type of traffic.
Very important traffic.
Scrolling down now through the Wireshark capture source IP address, destination IP address protocol
at layer three is OSPF.
So in other words, the protocol used at layer four, as we can see here, is OSPF or open shortest
path.
First let's have a look in the header.
It's OSPF version two.
It's a hello packet.
Here is the OSPF router source IP address.
In other words, that's the IP address on this interface.
OSPF area ID is backbone.
So area zero checksum is there password is set to the so we can actually see the password in the advertisement.
I'm going to jump to the other router and see if I can see a problem version is the same.
It's a hello.
First problem is right here.
Notice area id so first router backbone area second router area id is wrong.
That is a problem.
OSPF routers will not form neighbor relationships if the area IDs are incorrect, the area numbers have
to be the same.
Notice.
Also here, passwords are different.
So simple password authentication is used in both cases.
So in case I'm going to quickly notice, this is rather 1251.
Simple password authentication is used.
That is the password he has rather two.
Notice the IP address to five t simple password authentication is used, so that's good.
But notice the password is wrong.
This is uppercase OSPF, whereas the previous one is lowercase OSPF.
Passwords need to match for authentication to succeed.
So that is a problem.
And we have another problem, backbone area versus area one as soon as we see that there's a problem.
So to prove this, what I'll do is fix the network.
So here's rather one.
He has brought it to the let's fix the network and get it working.
So first thing.
Show IP route.
Notice we don't see OSPF routes in the routing table.
That tells us that there's a problem in the network.
On this side we are already seeing a whole bunch of error messages.
Notice mismatched area, backbone area.
So just by looking at the console of the router, we'll be able to see that there's a problem.
Show IP route also shows us that there are no OSPF routes in the routing table and we're getting this
message constantly.
So if we use the command show run pipe.
Section.
OSPF will be able to see the OSPF configuration or copy that and paste that into router one.
So notice here we've got OSPF router OSPF two router OSPF one.
That's fine.
They don't have to use the same process number.
Both Area zero and Area one in this example are using authentication on this route.
On the right hand side, all ten networks are an area one show IP interface brief shows us that the
routers configured with interfaces in the Ten Network.
So if I run that command again show run pipe section OSPF which shows us the OSPF configuration on the
router.
Both these interfaces, gigabit zero zero and gigabit zero one are going to be put into Area one, whereas
on this side, all interfaces are put into Area zero.
Another way to do this is to type show IP, OSPF interface and I'll do a brief because otherwise it's
too much information.
So brief.
Notice this interface gigabit zero one is an area zero.
This interface gigabit is zero zero is an area zero.
Both interfaces on area zero show IP OSPF interface brief.
On this side, both interfaces are in area one.
We can see that clearly over here.
And I mean, it's complaining like crazy the whole time about a mismatch.
So to fix this, what I need to do is remove this command and put the interfaces into area zero.
So I did a copy and paste there, delete that, change this to area zero.
So now show IP OSPF interface brief should show us that both interfaces are in area zero, which they
are.
So that's good.
So we fixed the area issue.
Let's run a short.
Kept you just so we can see that.
So.
I'll give you this as a second Wireshark capture.
So, OSPF, what we should see now is from router two in the header that the interface is an area zero
which we can see there.
And for the other router it's also in area zero.
So that's good, but it's not going to work because the passwords are wrong.
So we still need to fix the passwords once again.
Show IP OSPF neighbor.
Notice there's no neighbor relationship on router two and there's no OSPF neighbor relationship and
router one.
They don't form neighbor relationships because there's a problem with a password.
We could also do something like debug ip ospf adjacency to see the issue.
What's going on?
Notice right away we see the clear text mismatched authentication key debug IP OSPF age.
What we'll see here, hopefully something similar saying that there's a problem with the password.
There you go notice mismatched authentication key clear text.
So we know that we're using clear text authentication and we know that there's a password issue.
So show run on both sides will allow us to view what the password is set as can see it over there.
So gigabit to zero one.
And what I'll do at this point actually is just turn off debugging so we don't get those messages on
both sides.
So show run interface gigabit zero zero on the side, that interface notice the password is set to that.
And on this side, show run interface gigabit zero one.
This interface password is set to that, so let's make them the same.
So interface gigabit is zero zero.
I'll set the password to that just by copying it from router one.
So show run interface gigabit is zero zero.
Notice the password is the same and in my Wireshark capture notice we seeing.
Negotiations with database updates.
The routers are exchanging database information with each other because they formed a relationship that
wouldn't happen if there was a password mismatch.
Routers will only synchronize their databases or update one another if authentication passes and a bunch
of other things are right, including the area number.
So we fix two things.
We fix the area.
We fixed the password.
So at this point, I'll stop that Wireshark capture so it doesn't get too big.
And.
I'll save that.
As OSPF rts one fixed.
Okay.
But to prove it.
Notice on the rotors, a loading is full.
The side loading is full show IP route.
We see an OSPF network on this side.
Show IP route.
We see an OSPF network on the PCs.
Can they ping each other notice?
VM two can ping PC one.
So just to make the point, I have config.
This is the IP address of Windows two.
That's the PC over here and I'm pinging PC one.
So paying PC one PC one IP config IP address is this.
Can it ping PC two?
Yes, it can.
We fixed the issue in this network.
Two problems area number was wrong.
They need to be the same.
OSPF routers will not form neighbor relationships if the area numbers are different.
The password had to be the same.
Now it's really bad practice to use clear text authentication.
So once again, we can see the passwords in clear texture there.
It was still an issue.
Notice the password was wrong over here.
And then when I fixed it.
I might have to go a bit further.
So just before they started exchanging databases, the password should have been fixed.
So notice there is router two.
Password is the same as right of one.
Right to write a one password is the same.
And then they were able to exchange databases with one another.
In other words, form an OSPF relationship and exchange data.
Be careful with passwords again.
You don't want to use simple passwords like this.
You want to use MD5 passwords.
At least it's hashed.
It's not perfect, but it's better than this.
Anyone can capture these passwords and see what your device's passwords are and then inject routes into
the network.
Not a good idea.
Okay, so I'm hoping you enjoying these troubleshooting videos.
Let me know.