Core issue
When the mac-address is deleted on Catalyst 3750 (Cat3750) series switches, even when the mac-address is in the Address Resolution Protocol (ARP) cache, unicast packets flood.
This problem is seen in Cat3750 series switches that run Cisco IOS Software Release 12.2(25)SEE2 with a mac-address-table aging-time command value that is greater than the arp timeout command value.
For example, this problem is observed when the arp timeout command is set to the default value of 14400 seconds and the mac-address-table aging-time command is set to 28800 seconds.
This issue is documented in Cisco bug ID CSCsg21537.
Resolution
In order to workaround this issue, ping the next-hop device from the Cat3750 series switch.
Open a case with Cisco Technical Support with the TAC Service Request Tool for more assistance with this issue.
