Is the switch constantly flooding or is it periodically flooding (every 5 minutes) for an amount of time? Could be the cam table is full (maybe from mac spoofing or messed up aging timers) or maybe learning is disabled on the vlan (probably not). I'd check a couple things:
How does the cpu utilization look?
Is there any single port in the cam table that has an abnormally large amount of mac addresses?
Do a "sh spann vlan <#> detail" Is there an excessive amount of topology changes? topology changes will cause the switch to temporarily flood traffic.
A couple things you could do to address the symptoms, not necessarily the cause:
switchport block unicast (not sure if this is available on a 2960) on an interface will block all unknown unicast traffic
port security and/or dynamic arp inspection to address mac spoofing.
Sent from Cisco Technical Support iPad App