ARST-L2-000070 - The Arista MLS switch must have STP Loop Guard enabled on all nondesignated STP switch ports.

Information

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.

Solution

Configure the Arista MLS switch for STP Loop Guard globally with the following command:

switch(config)#spanning-tree guard loop default
switch(config)#

Alternatively, configure Loop Guard on each interface:

switch(config-if-Eth6)# spanning-tree guard loop

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Arista_MLS_EOS_4-2x_Y24M07_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5, CAT|II, CCI|CCI-002385, Rule-ID|SV-255972r882258_rule, STIG-ID|ARST-L2-000070, Vuln-ID|V-255972

Plugin: Arista

Control ID: dc493f308a55879352dd3e219c52fa190c4f8a8aafe9c3a669324f173da1613a