2009.8.17 Host flapping 02:01:00:00:00:00 & Microsoft NLB service

參考自 supportwiki.cisco.com

• The host is connected to ports x/y, and x/y runs a type of clustering or redundancy and has an issue with this mechanism.
  
  If the MAC address specified in the error message can be traced, this is likely the issue. For an example, refer to this error message:
  
  %C4K_EBM-4-HOSTFLAPPING: Host 02:01:00:00:00:00 in vlan x is flapping between port Gi x/y and port Gi x/y
  
  
  The MAC address 02:01:00:00:00:00 appears to be associated to Microsoft's Network Load Balancing (NLB) Service Heartbeat. It is suggested that the connected device (Microsoft host) be checked for causing these messages.