How Do I Configure Multi-Interface Loop Detection?
S series switches support MAC address flapping detection. MAC address flapping detection can detect loops formed among multiple interfaces. It is recommended that you configure multi-interface loop detection on downlink interfaces and set the action for interfaces with loops to alarm-only. When a loop is detected, the system sends a trap to the network management system to help locate the fault.
You can enable MAC address flapping detection in a VLAN to detect loops in the VLAN. All software versions support MAC address flapping detection in up to 32 VLANs.
[Quidway] vlan 3
[Quidway-vlan-3] loop-detect eth-loop block-time 30 retry-times 3
The alarm information includes the interface number, VLAN ID, and time. The system can display consecutive alarms and specific MAC addresses where flapping occurs.
#Jan 1 2008 06:53:12-08:00 Quidway L2IFPPI/4/MFLPIFRESUME:OID126.96.36.199.4.1.2011.5.25.160.3.2 Loop does not exist in vlan 3, Interface Ethernet0/0/1 resumed, block-time is 30 for mac-flapping disappeared.
#Jan 1 2008 06:52:22-08:00 Quidway L2IFPPI/4/MFLPIFBLOCK:OID188.8.131.52.4.1.2011.5.25.160.3.1 Loop exist in vlan 3, InterfaceEthernet0/0/1 blocked, block-time is 30 for mac-flapping, Mac Address is 00e0-fc22-765a.
In V200R003 and later versions, a switch considers that a loop has occurred on the network connected to an interface if detection packets sent from the interface are sent back to another interface. This mechanism can also be used for multi-interface loop detection.