29.7.6 Setting the failure monitoring time when link aggregation is used

When ring ports are configured using link aggregation, and a fault occurs for a port within the link aggregation transferring health check frames, control frames are discarded until link aggregation switching or degraded operation is completed. Therefore, when the fault monitoring time (health-check holdtime) of the master node is shorter than the time for completing link aggregation switching or degraded operation, the master node inadvertently detects a ring fault, and performs path switching. As a result, a loop might occur.

When ring ports are configured using link aggregation, the fault monitoring time for the master node needs to be set greater than the time for completing switching or degraded operation for the link aggregation.

Note that when LACP-based link aggregation is used, because the initial value of the LACPDU sending interval is long (30 seconds), when operation is performed without changing the initial value, a loop might occur. When using LACP-based link aggregation, either change the fault monitoring time for the master node, or set the LACPDU sending interval to short (one second).

Figure 29-41: Error detection when link aggregation is used