The ESXi host must enable Bridge Protocol Data Units (BPDU) filter on the host to prevent being locked out of physical switch ports with Portfast and BPDU Guard enabled.

BPDU Guard and Portfast are commonly enabled on the physical switch to which the ESXi host is directly connected to reduce the Spanning Tree Protocol (STP) convergence delay.

If a BPDU packet is sent from a virtual machine (VM) on the ESXi host to the physical switch configured as stated above, a cascading lockout of all the uplink interfaces from the ESXi host can occur. To prevent this type of lockout, BPDU Filter can be enabled on the ESXi host to drop any BPDU packets being sent to the physical switch.

The caveat is that certain Secure Socket Layer (SSL) virtual private networks that use Windows bridging capability can legitimately generate BPDU packets. The administrator should verify no legitimate BPDU packets are generated by VMs on the ESXi host prior to enabling BPDU Filter. If BPDU Filter is enabled in this situation, enabling Reject Forged Transmits on the virtual switch port group adds protection against Spanning Tree loops.

From the vSphere Client, go to Hosts and Clusters.

Select the ESXi Host >> Configure >> System >> Advanced System Settings.

Select the "Net.BlockGuestBPDU" value and verify it is set to "1".

or

From a PowerCLI command prompt while connected to the ESXi host, run the following command:

Get-VMHost | Get-AdvancedSetting -Name Net.BlockGuestBPDU

If the "Net.BlockGuestBPDU" setting is not set to "1", this is a finding.

From the vSphere Client, go to Hosts and Clusters.

Select the ESXi Host >> Configure >> System >> Advanced System Settings.

Click "Edit". Select the "Net.BlockGuestBPDU" value and configure it to "1".

or

From a PowerCLI command prompt while connected to the ESXi host, run the following command:

Get-VMHost | Get-AdvancedSetting -Name Net.BlockGuestBPDU | Set-AdvancedSetting -Value 1