found below from cisco website. Is this supported on Cat4? thanks!
How to Detect Excessive Flooding
Most switches implement no special command to detect flooding. Catalyst 6000 Supervisor Engine 2 and higher running Native IOS software 12.1(19)E and higher implements 'unicast flood protection' feature. In short this feature allows the switch to monitor the amount of unicast flooding per vlan and take specified action if flooding exceeds specified amount. Actions can be to syslog, limit or shutdown vlan - the syslog being the most useful for flood detection. When flooding exceeds the configured rate and the action configured is syslog, message similar to the following will be printed:
%UNICAST_FLOOD-4-DETECTED: Host 0000.0000.2100 on vlan 1 is flooding to an unknown unicast destination at a rate
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...