I couldn't find a solution to my problem in this group so I am posting this in hopes that you may find it useful.
Problem:
I started getting these messages in my cisco 3500xl cluster logs every minute.
%RTD-CLUSTER_MEMBER_7-1-ADDR_FLAP: FastEthernet0/9 relearning 6 addrs per min
sh mac showed a mac address of 0201.0000.0000 coming from FastEthernet0/9 along with the real mac of the nic card bound to the ip address. The host was a Windows 2003 server running the network load balancing service. This service was generating the
02:01:00:00:00:00 mac transmission.
Solution: go to network connection properties and look for the service named network load balancing and uninstall it. This will cause the server to disconnect for a moment so beware if you are using a remote console or your users are logged on.
ADDR_FLAP RTD-CLUSTER_MEMBER %RTD NLB Broadcom NetXtreme 5751 Gigabit Controller