We see many AP Impersonation alarms from WCS 4.1.83:
AP Impersonation of MAC '00:17:0f:xx:xx:xx' using source MAC '00:e0:98:xx:xx:xx' is detected by authenticated AP '00:17:0f:xx:xx:xx' on '802.11a' radio and Slot ID '0'.
Any ideas about this alarm? I have checked the source MACs in the alarm message are some client MACs.
These seem to be strictly bug related. Have a look;
CSCsb90622 AP impersonation alarms flooding the WCS
CSCsg01470 Add source address to AP-IMPERSONATION Trap. AP impersonation traps don't include the source MAC address. Format of the alarm message needs to be changed.
CSCsj50060 WCS use display wrong radio in AP Impersonation alarms. (shows 802.11a radio, even if 802.11a radio is off)
CSCsg44344 Add source address to AP-IMPERSONATION Trap. AP impersonation traps don't include the source MAC address. WCS currently only shows: AP Impersonation with MAC '00:14:1b:62:4e:42' is detected by authenticated AP '00:14:1b:62:4e:40' on '802.11b/g' radio and Slot ID '0'.
These bugs have been nicely documented by John in threads that date back a fair bit;
Hope this helps!