Cisco Switch – Understanding the MAC Address Learning Process

You probably don't have MAC flapping on the 4948. MAC flapping is where traffic from a MAC address is originated on more than one port in a short period of time. It seems to be happening on the 3650, but not happening on the 4948. This is specific to the switch, and the error will not be sent to other network devices.

That it is happening on one switch, but not the other, is a clue to help you troubleshoot where the problem may lie. This is probably caused by a layer-2 loop. You should investigate how the switches are connected, both directly and indirectly. There may be an STP misconfiguration on how the ports showing the MAC address are connected. This may be caused by someone plugging in a hub or dumb switch into multiple ports. Unfortunately, you may need physically check things out. Using portfast with BPDU guard on access ports may prevent this situation.

Here are the general steps on the Cisco switch:

1. Define VLANs 10 and 20 on the switch
2. Configure the port connected to the Meraki as a Trunk port, with VLAN 1 as the native VLAN (should be the default). Allow all VLANs on that port.
3. Configure the port connected to the device as an access port in VLAN 20
4. Change the management VLAN on the switch to VLAN 10
5. For all devices downstream from the Cisco switch, decide which VLAN you want them to use, and configure their ports as access ports in the chosen VLAN.