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Is spanning tree important in ethernet networks?

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Why is it important?

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What happens when you disable spanning tree?

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Are you carzy?

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So to help answer those questions I've got a packet tracer network consisting of two PCs.

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PC 1 and PC2 which are connected to layer 2 switches, these switches are running a default configuration

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and as you can see in Packet Tracer this interface is blocking.

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So in other words spanning tree is blocking on this port.

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We can see that by looking at the CLI of the switch.

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So show spanning tree, shows us that gigabit 1 02 has an alternate role in spanning tree under the current

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status is blocking.

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That means that for example pings from PC 1 to PC 2 will be sent across this link, gigabit 

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101 and not across gigabit

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102.

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BPD use or bridge protocol data units and some other management traffic will be sent and received on

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this port such as Cisco Discovery Protocol and Link Layer Discovery Protocol or CDP and LLDP

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but user traffic will not be received or transmitted under this port.

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So what happens if you disable spanning tree on both 
these switches?

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What will happen to the network?

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Now before I continue let me warn you.

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You use this packet tracer lab at your own risk if you disable spanning tree on switches as I'm going to

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do in this video your PCs CPU could go to 100 percent, packet tracer could crash and other nasty

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things could happen.

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So if you follow what I'm gonna do here the risk is entirely yours.

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So what do you think's going to happen when we disable spanning tree on both of these switches?

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How will traffic flow?

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So as an example if PC 1 sends a ping to PC 2 how will packets traverse the network?

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What will happen? To help demonstrate that you can use simulation mode in Packet Tracer

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and for this example, I'm only going to look at ARP and ICMP traffic.

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If you wanna try this yourself download the packet tracer file and use simulation mode in Packet

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Tracer but again doing what I'm gonna do here.

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Is done at your own risk.

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I'm now gonna demonstrate what happens when spanning tree is disabled on both these switches and

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show you how packets flow in the network.