Cisco 4500X - Troubleshoot dynamic mac address table entries disappearance

[Goncalo Catarino]

Hello,

I need some help to understand an issue that is ocurring on my network. We have two 4500X in VSS doing all the inter vlan routing. 

I've noticed a few weeks behind that i cannot connect to specific terminals, since PC's, printers and other devices from other VLAN than that device belongs. So the issue might be on the core switch.

On the 4500X, I do a ping to the address and therefore everything works fine for a time and eventually the problem appears again.

I checked the mac address table after the ping and i see the mac address of the device learned dynamic - > Can connect from every VLAN 

When the problem appears the mac address entry is not there anymore.

To solve this temporarly I made a script to ping the problematic IP addresses from time to time to populate the mac address table on the 4500X, but i cannot understand why this is happening.

Can anyone please help me to understand this?

Thanks in advance

[Philip D'Ath]

The the MAC address is not in the forwarding table the switch will flood it out every port, so a missing MAC address on its own will not cause the issue.

I would check that everything has the correct subnet mask and default gateway.  One of these two might be mis-configured and proxy-arp might be working enough to hide the true issue.

[Goncalo Catarino]

Thanks for your reply. 

I checked, and every device has the correct mask and gateway. This really doesn't make sense. 

[med.talbi]

Hello Goncalo Catarino,
Did you find a way for this problem please ?
I get this problem too!! my version is 03.09.00.E

[med.talbi]

This is cisco Bug : CSCvb78700
Ater upgrading to 03.09.02 the problem was solved.

[jeffrey.ye]

My version is the same with you, and has the same problem too