What changed in Arista MLS EOS 4.X L2S STIG V2R3V2R3 changes

Check text

Review the Arista MLS switch configuration to verify that STP Loop Guard is enabled. It can be enabled globally or applied to an interface. Note: Arista uses STP Loop guard to protect against one-way connections. switch# sh run | sec spanning-tree spanning-tree guard loop default Or, interface Ethernet6 spanning-tree guard loop If STP Loop Guard is not configured globally or on nondesignated STP ports, this is a finding.

Discussion

The Spanning Tree Protocol (STP) loop guard feature provides additional protection against STP loops. An STP loop is created when an STP blocking port in a redundant topology erroneously transitions to the forwarding state. In its operation, STP relies on continuous reception and transmission of BPDUs based on the port role. The designated port transmits BPDUs, and the nondesignated port receives BPDUs. When one of the ports in a physically redundant topology no longer receives BPDUs, the STP conceives that the topology is loop free. Eventually, the blocking port from the alternate or backup port becomes a designated port and moves to a forwarding state. This situation creates a loop. The loop guard feature makes additional checks. If BPDUs are not received on a nondesignated port and loop guard is enabled, that port is moved into the STP loop-inconsistent blocking state. In topologies where fiber optic interconnections are used, physical misconnections can occur that allow a link to appear to be up when there is a mismatched set of transmit/receive pairs. When such a physical misconfiguration occurs, protocols such as STP can cause network instability.

V-255972 in V2R3