MAC flapping on physical switches due to duplicate Bare Metal Edge uplink MAC addresses in NSX

Products

• VMware NSX

Issue/Introduction

• Conflicting MAC addresses are configured on T0 uplink interfaces of Bare Metal Edge nodes that are being managed by 2 completely different NSX environments.
• The uplink interfaces with the conflicting MAC address are configured in same Broadcast domain (same VLAN) in these different NSX environments.
• Due to these conflicting MAC address assignment and uplink in same L2 domain, mac flapping is observed on the TOR switch resulting in network disruption.

Environment

VMware NSX

Cause

Currently for Bare Metal(BM) Edges, NSX-T uses a fixed range MAC address pool for allocating MAC. When Bare Metal Edges are deployed in different NSX instances, the uplink interfaces of T0 gateway may get assigned the same MAC address.

Resolution

This is an expected behavior.

Follow below workarounds to get this resolved:

• Segregate the VLANs of the uplink interfaces configured in 2 different NSX deployments.
  
  
• Delete the existing uplink interface with conflicting MAC address, and recreate the same. A different MAC address may get allocated upon reconfiguration.

Additional Information

• This behavior is also applicable to Tunnel Endpoint (TEP) MAC addresses allocated to TEPs of Bare Metal Edges deployed in two different NSX environments.

• For more information on TEP MAC conflicts, refer to:  Bare metal edges from separate NSX-T deployments getting configured with same TEP MAC