The Arista MLS layer 2 switch must have BPDU Guard enabled on all switch ports connecting to access layer switches and hosts.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-255971	ARST-L2-000060	SV-255971r882255_rule		Medium

Description
If a rogue switch is introduced into the topology and transmits a Bridge Protocol Data Unit (BPDU) with a lower bridge priority than the existing root bridge, it will become the new root bridge and cause a topology change, rendering the network in a suboptimal state. The STP PortFast BPDU guard enhancement allows network designers to enforce the STP domain borders and keep the active topology predictable. The devices behind the ports that have STP PortFast enabled are not able to influence the STP topology. At the reception of BPDUs, the BPDU guard operation disables the port that has PortFast configured. The BPDU guard transitions the port into a disabled state and sends a log message.

Description

If a rogue switch is introduced into the topology and transmits a Bridge Protocol Data Unit (BPDU) with a lower bridge priority than the existing root bridge, it will become the new root bridge and cause a topology change, rendering the network in a suboptimal state. The STP PortFast BPDU guard enhancement allows network designers to enforce the STP domain borders and keep the active topology predictable. The devices behind the ports that have STP PortFast enabled are not able to influence the STP topology. At the reception of BPDUs, the BPDU guard operation disables the port that has PortFast configured. The BPDU guard transitions the port into a disabled state and sends a log message.

STIG	Date
Arista MLS EOS 4.2x L2S Security Technical Implementation Guide	2023-01-11

Details

Check Text ( C-59647r882253_chk )
Review the Arista MLS to verify that BPDU Guard is enabled on all user-facing or untrusted access switch ports. switch#show run \| section bpdu interface Ethernet37 spanning-tree bpduguard enable If the Arista MLS switch has not enabled BPDU Guard, this is a finding.

Fix Text (F-59590r882254_fix)
The Arista MLS switch provides the capability to configure "spanning-tree bpduguard". Configure the Ethernet interface commands: config interface Ethernet[X] switch(config)#interface ethernet [X] switch(config-if-Et[X])#spanning-tree bpduguard enabled switch(config-if-Et[X])