Microsoft network load balancer (NLB) Unicast or Multicast mode on NSX overlay.

Products

• VMware NSX

Issue/Introduction

• Deploying a Microsoft network load balancer in an NSX overlay environment.
• In NSX-V it was possible to make this work by adding static ARP entries, however this is not possible in VMware NSX.
  
  

Environment

VMware NSX

Resolution

Currently using Microsoft network load balancer (NLB) in unicast or Multicast mode is unsupported on NSX overlay:

• In Multicast mode, It should work if clients and NLB VIP are connected to the same segment but not for routed traffic (which would require a static ARP entry which is not supported).
• When deployed in unicast mode, Microsoft NLB overwrites the physical MAC addresses of participating nodes with a unified cluster MAC address. Consequently, NSX experiences MAC learning conflicts across multiple VM segment ports, preventing the network switch from accurately determining port-to-MAC associations.