Cisco Switch MAC address Table

[mediaos718]

I have been having layer 2 issues on the network. Some devices (Motorola radio repeaters, and Fortecho RFID's ) MAC addresses are not showing up on the our Cisco switches (3500's, 3750's, 3850's, and 9300). The issue is random - We have a switch (9300) where the devices always work. Cisco TAC and the manufacturers do not know what is going on. Does anyone else also experience the same problem.

[Philip D'Ath · Accepted solution]

Some things to consider.

The switch leans the MAC address of a device on a port when the device generates a packet.  If devices only receive packets it's possible the switch wont get a chance to learn what the MAC address for the device plugged into the port is.

Secondly if the port transitions to a down state (even if only briefly) the learned MAC address will be dumped.  This can sometimes happen with devices with power saving settings trying to save power by downshifting their ports to 10Mb/s when idle.  Energy Efficient Ethernet is another related feature of devices.