218 | Stackingw w w . d e l l . c o m | s u p p o r t . d e l l . c o m Master Switch FailsProblem: The master switch fails due to a hardware fault, software crash, or power loss.Resolution: A failover procedure begins:1. Keep-alive messages from the Aggregator master switch time out after 60 seconds and the switch isremoved from the stack.2. The standby switch takes the master role. Data traffic on the new master switch is uninterrupted.Protocol traffic is managed by the control plane.3. A member switch is elected as the new standby. Data traffic on the new standby is uninterrupted. Thecontrol plane prepares for operation in Warm Standby mode.Stack-Link Flapping ErrorProblem/Resolution: Stacked Aggregators monitor their own stack ports and disable any stack port thatflaps five times within 10 seconds. If the stacking ports that flap are on the master or standby,KERN-2-INT error messages note the units (Figure 17-28).To re-enable a downed stacking port, power cycle the stacked switch on which the port is installed.Figure 17-28. Recovering from a Stack-Link Flapping ErrorMaster Switch Recovers from FailureProblem: The master switch recovers from a failure after a reboot and rejoins the stack as the standby unit.Protocol and control plane recovery requires time before the switch is fully online.Resolution: When the entire stack is reloaded, the recovered master switch becomes the master unit of thestack.--------------------------------------MANAGMENT UNIT-----------------------------------------Error: Stack Port 49 has flapped 5 times within 10 seconds.Shutting down this stack port now.Error: Please check the stack cable/module and power-cycle the stack.10:55:20: %STKUNIT1-M:CP %KERN-2-INT: Error: Stack Port 50 has flapped 5 times within 10seconds.Shutting down this stack port now.10:55:20: %STKUNIT1-M:CP %KERN-2-INT: Error: Please check the stack cable/module andpower-cycle the stack.---------------------------------------STANDBY UNIT------------------------------------------10:55:18: %STKUNIT1-M:CP %KERN-2-INT: Error: Stack Port 50 has flapped 5 times within 10seonds.Shutting down this stack port now.10:55:18: %STKUNIT1-M:CP %KERN-2-INT: Error: Please check the stack cable/moduleand power-cycle the stack.
