Is spanning tree important in ethernet networks?
Why is it important?
What happens when you disable spanning tree?
Are you carzy?
So to help answer those questions I've got a packet tracer network consisting of two PCs.
PC 1 and PC2 which are connected to layer 2 switches, these switches are running a default configuration
and as you can see in Packet Tracer this interface is blocking.
So in other words spanning tree is blocking on this port.
We can see that by looking at the CLI of the switch.
So show spanning tree, shows us that gigabit 1 02 has an alternate role in spanning tree under the current
status is blocking.
That means that for example pings from PC 1 to PC 2 will be sent across this link, gigabit
101 and not across gigabit
102.
BPD use or bridge protocol data units and some other management traffic will be sent and received on
this port such as Cisco Discovery Protocol and Link Layer Discovery Protocol or CDP and LLDP
but user traffic will not be received or transmitted under this port.
So what happens if you disable spanning tree on both these switches?
What will happen to the network?
Now before I continue let me warn you.
You use this packet tracer lab at your own risk if you disable spanning tree on switches as I'm going to
do in this video your PCs CPU could go to 100 percent, packet tracer could crash and other nasty
things could happen.
So if you follow what I'm gonna do here the risk is entirely yours.
So what do you think's going to happen when we disable spanning tree on both of these switches?
How will traffic flow?
So as an example if PC 1 sends a ping to PC 2 how will packets traverse the network?
What will happen? To help demonstrate that you can use simulation mode in Packet Tracer
and for this example, I'm only going to look at ARP and ICMP traffic.
If you wanna try this yourself download the packet tracer file and use simulation mode in Packet
Tracer but again doing what I'm gonna do here.
Is done at your own risk.
I'm now gonna demonstrate what happens when spanning tree is disabled on both these switches and
show you how packets flow in the network.