ESXi Uplink Experiences High Inbound Traffic During VM Deployment

Products

• VMware vSphere ESXi
• VMware vCenter Server

Issue/Introduction

• An ESXi host vmnic experiences high inbound traffic spikes (peaking at ~5.4 Gbps) on the physical interface pinned to the Management network .
• Traffic spikes coincide with virtual machine deployment tasks, specifically when copying or cloning data from an NFS source template to local vSAN storage.
• Physical switch monitoring reports saturation on the port connected to the host's management uplink.

Environment

VMware vSphere ESXi

VMware vCenter Server

Cause

The ESXi host uses the vmk0 (Management) interface to retrieve VM template data from the NFS server because it lacks a VMkernel interface on the same subnet as the NFS storage. This forces storage traffic to follow the default route via vmk0.

Resolution

By providing a local subnet route to the NFS storage, the host bypasses the default gateway (vmk0). This prevents bulk data transfer from competing with management traffic on vmnic and utilizes more appropriate paths for storage traffic.

1. Configure a new VMkernel interface on the ESXi host.
2. Assign the new interface an IP address within the same subnet as the NFS server to ensure local L2 routing.
3. Isolate traffic if required by mapping this VMkernel interface to a dedicated vSwitch or portgroup using different physical uplinks (vmnics) to prevent management network saturation.