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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-239312	ESXI-67-000058	SV-239312r674865_rule		Low

Description
BPDU Guard and Portfast are commonly enabled on the physical switch to which the ESXi host is directly connected to reduce the STP convergence delay. If a BPDU packet is sent from a virtual machine on the ESXi host to the physical switch so configured, 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 SSL VPNs that use Windows bridging capability can legitimately generate BPDU packets. The administrator should verify that there are no legitimate BPDU packets generated by virtual machines 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.

Description

BPDU Guard and Portfast are commonly enabled on the physical switch to which the ESXi host is directly connected to reduce the STP convergence delay. If a BPDU packet is sent from a virtual machine on the ESXi host to the physical switch so configured, 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 SSL VPNs that use Windows bridging capability can legitimately generate BPDU packets. The administrator should verify that there are no legitimate BPDU packets generated by virtual machines 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.

STIG	Date
VMware vSphere 6.7 ESXi Security Technical Implementation Guide	2022-01-05

Details

Check Text ( C-42545r674863_chk )
From the vSphere Client, select the ESXi host and go to 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.

Check Text ( C-42545r674863_chk )

From the vSphere Client, select the ESXi host and go to 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.

Fix Text (F-42504r674864_fix)
From the vSphere Client, select the ESXi host and go to 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 commands: Get-VMHost \| Get-AdvancedSetting -Name Net.BlockGuestBPDU \| Set-AdvancedSetting -Value 1