MTU mismatch alert on One-Arm Load Balancer attached to segment VLAN

Products

• VMware NSX

Issue/Introduction

• One-Arm Load Balancer attached to segment VLAN has been configured.
• Because it is a VLAN segment, the underlying VDS has been configured with an MTU of 1500.
• Following alert is raised in NSX manager UI:
  
  mtu_check.mtu_mismatch_within_transport_zone

Environment

VMware NSX

Cause

‌Even though the business uses a VLAN segment, the MTU will not exceed 1500, but the NSX Edge Node will still use the overlay network for the heartbeat of the Edge Node cluster. The packets of the overlay network will exceed 1500.

Resolution

According to the documentation, configure the underlying VDS of the overlay network with an MTU of 1700. Guidance to Set Maximum Transmission Unit