About Loop Detection

The loop detection feature enables you to detect the presence of loops in an OLO network, either at the port (link-level loop detection) or the tunnel level (tunnel-level loop detection). Use it to determine if there are any untagged frames on a network or if a loop is present in a specific VLAN. Loop detection on UNI, ENNI and INNI interfaces is supported. Any loops that are detected are reported through SNMP traps (i.e. alarms) that can be viewed in the Show ►Alarm page of the management Web interface. One alarm entry is created for each loop detection instance, which can be individually configured in the System ►Alarm ►Configuration page.
You can also test for loopbacks manually and using the Loop Detection Diagnostic Tool.
The design of the loop detection feature involves certain limitations. A loop detection instance can be created on physical and logical ports, but not on LAG ports.

• If a loop detection instance is created on a physical port, the LAG port containing the physical port cannot be activated using LACP or Link Status protection.
• If a loop detection instance is created on a logical port, the protection mode must be set to LACP or Link-Status. If a protection mode is enabled, the loop detection instance must be disabled before the protection mode can be disabled.
• If a LAG port is enabled, a loop detection instance cannot be created on a port that is part of that LAG port.

Furthermore, ERP protection mode is not supported with loop detection.

• If a loop detection instance is created on a logical port with LACP or Link Status protection mode, and the port configuration is subsequently changed to ERP protection mode, the loop detection instance will be disabled.
• If a loop detection instance is created on a physical port with the LAG port activated using ERP protection mode, the loop detection instance will be disabled.