ARST-L2-000150 - The Arista MLS layer 2 switch must enable Unidirectional Link Detection (UDLD) to protect against one-way connections.

Information

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.

Solution

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:

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

Note: UDLD is a Cisco-proprietary protocol. However, other switch vendors, such as 3Com, Extreme, and D-Link, have similar functionality in their products, respectively: Device Link Detection Protocol (DLDP), Extreme Link Status Monitoring (ELSM), and D-Link Unidirectional Link Detection (DULD).

See Also

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

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b., CAT|II, CCI|CCI-000366, Rule-ID|SV-255978r882276_rule, STIG-ID|ARST-L2-000150, Vuln-ID|V-255978

Plugin: Arista

Control ID: 300f659933bd2e25e94246935618050bc0ae1d68e1a684bfbea89d56c25336bf