Learn the basics of BPDUs

 

In this session, we will learn about the concept and operating principles of BPDU.

 

 

1. What is BPDU?

 

 

BPDU Guard refers to the port shutdown (err-disable) state when a BPDU is received through a port to which the BPDU Guard is applied.

 

In general, End Device equipment does not need to receive BPDUs from Spanning-tree, nor does it need to transmit them. Rather, sending BPDUs from the End Device means that it intentionally attacks or leaks into security.

 

 

It also prevents STP's BPDUs from being looped by incorrectly connecting the UTP cable when users use the Switch in-house. BPDU received on a port on which BPDU Guard is enabled.

 

 

When a BPDU is received on a port on which the BPDU Guard on the switch is set as shown in the figure, the port is shut down as soon as it is in the Err-disable state.

 

If you want the Err-disable state to be original by the BPDU Guard, you can do no shutdown on that port.

 

 

- Two ways to set up BPDU Guard

 

1. Global Configuration mode Switch(Config)# spanning-tree portfastbpduguarddefault

▶ Apply the BPDU Guard only on the interface where Portfast is set.

 

2. Interface mode Switch(Config)# interface fastethernet0/2 Switch(Config-if)# spanning-tree bpduguardenable

▶ Enable bpduguard on the interface.

 

 

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