On our 4506 switch I am getting the following errors:
Jul 15 09:17:00 CDT: %C4K_EBM-4-HOSTFLAPPING: Host 00:20:E0:CC:56:E9 in vlan 21
is flapping between port Fa2/3 and port Fa2/6
Jul 15 09:21:34 CDT: %C4K_EBM-4-HOSTFLAPPING: Host 00:20:E0:CC:56:E9 in vlan 21
is flapping between port Fa2/6 and port Gi1/1
The MAC address is a wireless terminal and the Ethernet ports have Intermec APs connected to them. The Gi1/1 is an uplink to our core switch where other access switches are connected and those switches have their own APs.
Cisco docs say it's spanning tree but STP is enabled on the switches. It only happens on the 4506. The 3750 switches don't have these errors.
Problem seems to be related to the roaming of the terminals. But roaming happens normally so I'm not sure why it's an issue on the 4506.
Any thoughts are appreciated.
Is it because the logging level on the 3750 switches may set to log only high severity messages. (something to greater than 4)? If it is the 3750's wouldn't be generating the 'warning' message as it did with the 4506.
That's because the 3750 doesn't see the MAC address on different ports like the 4506 does, or else you would see exactly the same message. It sounds like the wireless terminal is associating to different AP's and subsequently the MAC address is seen on different interfaces on the 4506. Is this wireless terminal stationary or mobile? If it is stationary I might suggest that it is not normal. Wireless clients tend to be very "sticky" with respect to the AP. If it is constantly roaming from one to the other I might think you have some kind of problem in the wireless environment.
this is not really an error message, in this case.
Because of roaming the wireless end devices are visible several switchport. It takes some time before the switch clears its forwarding table. The mac address of the wireless client is visible in the "old" forwarding table but in real it is connected to another access port and switchport.