Okay so let's see if we can answer these questions.
First question is, Is CDP enabled on the switches?
What I'll do is do a search for CDP and in CDP we can see that there are three switches sending messages.
So I would say the switches have CDP enabled on them.
I mean we can look at say the first switch.
Look at the details and we can see this switch has this name SharkS1, here's another switch Shark
S2 and here's a third switch
SharkS3.
So I would say these three switches have CDP enabled on them.
Another hint is notice the interface number, gigabit 03.
That's this interface, that's shark3.
This switch Shark2 is connected via gigabit 02.
That's this interface and this switch Shark1 is connected via this interface to the hub gigabit
01.
So I would say it's this switch.
So I would be inclined to say we can confirm this, that this switch is called Shark
S1, this switch is called SharkS2 and this switch is called SharkS3 and let's be consistent
where I put the names. So those are our three switches and once again I was able to determine that by looking
at the Wireshark captures. I'll make these a bit smaller
so that we can have them all on the screen at the same time.
So once again SharkS1, so Cisco switch
it's connected to the network on gigabit 01.
Remember this is a hub.
So we're seeing all these messages on this interface over here.
In other words, if I was running Wireshark directly on this Ubuntu device I would see all of these messages
in the same way that I'm seeing them now. Switch 2, SharkS2
interface is gigabit 0
2 see that over there and then if we go back to the third switch gigabit 03 that is switch
SharkS3.
Okay, so first question, is CDP enabled?
I would say yes it is
So answer here would be yes.
What about LLDP? Just search for a LLDP.
Notice LLDP is enabled.
We see first switch, second switch, third switch
and if we look at the LLDP messages.
Notice Shark1 gigabit 01, Shark2 gigabit 02, Shark3 gigabit 03.
So I would say LLDP is enabled on those three switches.
Can we name the switches?
Yes, we can.
We've got SharkS1, SharkS2, SharkS3 and I've already shown you the names in the topology.
What type of devices are these?
So looking at say LLDP we can see the Cisco
IOSv IOS layer 2 switches and there's the version of operating system.
So I won't bother writing them running it out but V
IOSv layer2 switches and we can specify the version over there, notice vIOS layer 2 or IOSv
layer 2 is the type of switch.
These are VIRL images running within gns3 and there's the operating system. I mean we could also
go look at the capabilities and see more capabilities of the device such as it's capable of being
a router
it's capable of being a bridge.
In other words, it's a router and a switch, layer 2, layer 3 switch. Okay, so which VTP domain
is it part of? Now in LLDP.
You may not see VTP because VTP is a Cisco proprietary protocol.
So let's have a look at CDP, in CDP we see
address information.
There was also one other question, so I'll answer that in a moment.
But notice the VTP domain is Sharks. So VTP domain here Sharks, IP address switches and I won't bother
writing that all out.
We can simply work it out together,
first switch IP address 192 168 1.1, second switch
192 168 1.2 and third switch 192 168 1.3. So let's confirm that through the console, just
to show you that what we have been looking at is correct.
So here's switch 1, called SharkS1 show IP interface brief IP address is that
switch 2 show IP interface brief
IP address is that as we worked out and switch 3 show IP interface brief
there's the IP address.
Okay, so show CDP neighbors we can see both switch 1 and switch 2 in other words CDP is running on this
switch and the other switches and show LLDP neighbors shows us something similar we can see the other
switches. So we have proven this through Wireshark and I've shown you this through the CLI that CDP is
enabled LLDP is enabled there are the switch names, operating system is this, you could do show version
here just to prove it.
Notice there is what we're seeing through the CDP messages.
In other words through the Wireshark captures.
Okay, so on switch one show VTP status.
Notice domain is sharks but actually looking at the other switches
was that correct? Show
CDP status
so notice there's no domain name set on switch 2 and there's no domain name set on switch 3.
That was a mistake that I made I should have said that manually, so VTP domain is sharks on switch one
but is null on switch 2 and switch 3.
Let's go back to the Wireshark capture. So on switch 2 do we see a VTP domain.
Notice it's blank but on switch 1, it's sharks, switch 2 it's blank, switch 3 it's blank or null.
Now the reason the other switches didn't learn
about the VTP domain is there are no trunks on the switches, so switch 1 as an example doesn't have
trucking enabled on its ports and the same is true on switch 2 these ports have to be trunk ports for
VTP messages to be advertised.
Okay so but of a trick there.
I made that mistake of not looking carefully at the Wireshark messages.
How did you get on?
Were you able to work this out?
Did you get similar answers?
It's important as always to be able to read Wireshark messages and don't make the mistake that I made
here of assuming that because something goes in one message that it's the same for others.