In this example, we've got two switches and four routers which are acting as PCs in the topology.
We've also got a hub which I'm going to use to capture traffic using Wireshark.
These devices have just booted up, so they have no configuration.
On the first switch, I'll give the switch a hostname of one and on the second switch, give it a hostname
of S2.
Show.
VLAN.
At the moment we only have one ethernet of VLAN configured VLAN one.
All ports in the switch are configured in that VLAN.
Cisco switches also have some older VLANs by default 1002, three, four and five, which were used
previously for FTI and token ring.
Those VLANs are not used any more today.
Switch to shows something similar.
So show vlan brief.
We have vlan one.
All ports are configured in VLAN one.
Here's rather one which is acting as our PC.
I'm going to configure the first Ethernet interface with an IP address of ten 111.
Slash 24 musk and I'll no.
Shut the interface.
On rather to do something similar.
No.
Shut the interface given an IP address of ten 112.
So without any further configuration, we should be able to ping between rather one and rather two.
Notice rather to can ping write a one and write a one.
Can ping rather to the switches.
Just have a default config.
All ports on the switches are in VLAN one.
We can see that by using the command show interface gigabit or zero zero switch port.
The support gigabyte zero zero is using administrative mode.
Dynamic auto operational mode at the moment is static access negotiation of trunking is on.
In other words, FTP is enabled.
But at the moment because there is no switch to negotiate with.
The port is in VLAN one the default VLAN.
Now we can see the traffic by doing a CAPTCHA using Wireshark.
Various traffic is seen here.
We've got a spanning tree beeped you being sent by the switch we can see Cisco discovery protocol messages
being sent by the switch as well, showing the switch port, the platform and other information.
But what I'd like you to see is all traffic is Ethernet frames.
There is no 2 to 1 queue tagging on these frames.
Let's do a search for ICMP traffic.
At the moment there is no ICMP traffic.
I'll get rather one to ping root of two and notice we see the ICMP traffic.
What you'll notice is we have the source Mac address of router one.
Pinging routed to.
Protocol type is IP version for source.
IP version for addresses ten 111.
Destination IP Addresses ten 112.
It's a standard Ethernet frame encapsulating IP and ICMP.
In this case, it's an echo and the reply is an echo reply.
There is no Ethernet tagging on this frame at all.
It's a standard Ethernet frame.
There is no concept of VLAN either.
No VLAN information is transmitted on the frames.
Even the other frames such as CDP don't show any VLAN information whatsoever.
We'll stop that capture.
This is an access port and this is an access port by default.
The same will be true on switch two.
I'll configure router three with an IP address of ten.
One one, two, three.
Shut the interface and I'll do something similar on right of four.
Shut.
IP address ten 114.
Ken wrote for ping router three.
Acting as host three.
Yes, it can.
Start a CAPTCHA here.
We can see various traffic types being captured, including once again CDP en route of three, helping
route of four.
Ping succeeds.
I'll filter for ICMP.
And once again, you can see that this is a standard Ethernet frame.
There is no information about VLANs contained in these frames, just standard Ethernet frames.
So the PCs in the topology are unaware of any VLAN information.
They are sending untagged frames.
In other words, standard ethernet frames to the switches and the switches are sending untagged frames
to the PCs.
Now let's concentrate on switch one for the moment.
I'm going to set the HTTP mode of the device to transparent, which means it won't try and synchronize
VLAN information with the other switch.
Shovlin once again shows us that we have one ethernet vlan configured.
Let's create VLAN two.
Show VLAN brief.
We now have two ethernet vlans, but no ports are configured in VLAN two.