As the Nexuus 2K are fex switches they are not typical switches. They are essentially external line cards. FEX's can't be connected to another switch, just end user devices. Technically this is because if it receives a BPDU the port will go into an error disabled state. I am fairly sure this is what is happening, however, the service provider will be able to give you the cause as BPDUerror. I imagine the Meraki MX is passing through a BPDU received on the LAN ports out of the WAN ports which is triggering the error. If so I can only think of 3solutions (not saying these are best)   1) Confirm, it is a BPDU and then confirm via a packet trace that the MX is forwarding it out the WAN port. If so raise a case with meraki as I don't believe the MX should be doing this? 2) Convert it to a routed port if possible as a routed port won't send BPDUs. This may not work with your service provider network. 3) Ask your service provider to allow bpdu to be sent on the port. They won't like that though and it's not best practice. ... View more