We appear to be experiencing a similar issue on a stack of Cisco Catalyst 2960S (IOS:15.0(1)SE2. is there a pattern in the source address in the sniffer trace that see's unicast flooding? is there any port security or similar mechanism or straight? does the 0050.56 mac appear? Have you ever seen it disappear? or have you resolved it with the higher mac aging? (run the #sh mac address-table address over and over until you see flooding on the sniffer) Let's focus on the issue at hand, where you ran a sniffer trace on the 2960 and saw the unicast flooding. Run it a few times in a row to make sure aging is not changing.
#sh mac-address-table aging vlan -> should see 300seconds (if default) (I am assuming that there is no relationship between the flapping SLB MAC and the VM MAC you are focused on.) Flapping due to SLB should be fixed but should not cause other switches to "fast age" their mac tables, unless a TC (topology change occurs) The key is to understand that the switch should not age out the whole mac-address table, only flag that address.ī. You are correct in that when this address flaps, and if there's traffic destined for the client you will see temporary flooding. > no big issues if the mac-address flap is for this and is not frequent. This will hold the mac untill the ARP expires, so if there is really no traffic ARP will purge out too.
Configure below command and should take care of it. If you encounter any off the above issue. Seperate vlans using different HSRP gateways for redundancy and loadbalance (sort of asymmetric routing) No incoming traffic from the destination machine ( usually incase of backup server as they dont send out any network traffic).Ĥ. mac sync issue between DFC and SP (6500 stuff !!!)ģ. Asymmetric path between source and destination.Ģ. Some of the known reason why switch would not learn or flush the mac-address are belowġ. Meaning that the originating device sends a complete unicast traffic to the switch, but switch does not have dest mac in mac table. Switch starts to flood unicast traffic when it does not know or learns about the destination mac in the CAM table.
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