Core issue
These messages indicate that the MultiLayer Switching (MLS) table on your Catalyst is deleting specific multicast flows.
The multicast messages may look similar to this:
%MCAST-6-DELGDA:Deleting a GDA 01-00-aa-bb-cc-dd in vlan
This means that an Internet Group Management Protocol (IGMP) leave was received by the route processor from the last receiver in this specific multicast group, in this VLAN.
%MLS-6-MCAST_L3FLOW:Delete from the Route Processor N.N.N.N for Source N.N.N.N Group 255.255.255.253 Vlan
The means that the flow has been purged from the MLS table because it has been inactive and timed-out.
Both of these are normal operations and are expected to be seen if you have your logging level set past 5.
Resolution
These messages appear whenever the logging facility is set to 6 or higher and the messages are informational only.
To set the facility and severity level used when logging system messages, use the set logging level mcast 4 command. The severity level is a single digit from 0 to 7 that reflects the severity of the condition.
For multicast environments, bringing the logging level of the mcast facility up to 4 is recommended so that syslog messages are produced if router ports are deleted. Before CatOS 5.5(5) this could result in syslog messages being recorded for IGMP joins and leaves, which is too noisy to monitor.
Error message
%MCAST-6-DELGDA:
%MLS-6-MCAST_L3FLOW:
