2960X MAC table not updating

[phonedude54956]

Over the last few months I have had several 2960X stacks stop working for newly attached devices. The mac table does not update with the new address. I do however see the mac address of the device on the core switch, in the correct VLAN and coming from the correct port channel. I also see the dhcp process worked because I have an ARP entry for that mac address.

Once the switch is rebooted, everything works as expected - mac table updates and devices gets it dhcp addresses and start talking.

I had a TAC case opened a few months ago but there was no resolution. 

Has anyone else seen this type of behavior?

[Kallol Bosu]

Hello,

I just wanted to get the understanding correct about your problem- 

Lets say you have a new device attached to 2960X stack and the stack is connected to CORE through a PO. Do you mean you see the MAC entry on CORE but not on stack? 

!

What happens when you clear the ARP/CAM cache on CORE? Do you see the MAC/ARP is built on CORE correctly but 2960x stack does not show any entry? Does the ping go through? I hope the end host is not connected to any other switch apart from the stack in question, right? (I meant through a different NIC or so). Do you see the problem when a PC is attached to the switch port? Lets assume port X is not learning any MAC but ping from CORE goes through, do you the see that packet is flooded by 2960X stack? 

!

If that is the case, I would like to look at few outputs from switch stack in problematic situation- 

- show version

- show run interface <affected interface>

- show mac address-table address <mac-address> all

- show mac address-table address interface <>

- show interface <> 

- attach or session into each member of stack and run the command "show mac address-table <address>" from each member of stack. 

- show mac address-table | i <address>

- test mvlan show all

Please rate this post if helpful

Regards,

Kallol