The Arista MLS layer 2 switch must enable Unidirectional Link Detection (UDLD) to protect against one-way connections.
An XCCDF Rule
Description
<VulnDiscussion>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. UDLD is a layer 2 protocol that can detect these physical misconfigurations by verifying that traffic is flowing bidirectionally between neighbors. Ports with UDLD enabled periodically transmit packets to neighbor devices. If the packets are not echoed back within a specific time frame, the link is flagged as unidirectional and the interface is shut down.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-255978r882276_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Configure the Arista MLS switch to enable Loop Guard to prevent Unidirectional Link Detection (UDLD) and to protect against one-way connections.
switch(config)#spanning-tree guard loop default
switch(config)#
Alternatively, configure Loop Guard on each interface: