Troubleshooting Network Performance Issues in a vSphere Environment

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

• Networking performance to and from the host and/or virtual machines is not optimal
• Network performance is slow

Cause

Network problems can have several causes: 

• Virtual machine network resource shares are too few.
• Network packet size is too large, which results in high network latency. Use the VMware AppSpeed performance monitoring application or a third-party application to check network latency.
• Network packet size is too small, which increases the demand for the CPU resources needed for processing each packet. Host CPU, or possibly virtual machine CPU, resources are not enough to handle the load.

Resolution

There are many ESXi host components that can contribute to network performance.

Validate that each troubleshooting step below is true for the environment. The steps provide instructions or a link to a document, for validating the step and taking corrective action as necessary. The steps are ordered in the most appropriate sequence to isolate the issue and identify the proper resolution. Please do not skip a step.

1. Verify that the latest version of VMware Tools is installed in the virtual machines. For more information, see Verifying a VMware Tools build version and Overview of VMware Tools.
2. VMware recommends using multiple NICs on the associated virtual switch to increase the overall network capacity for portgroups that contain many virtual machines or several virtual machines that are very active on the network. For more information, see NIC teaming in ESXi and ESX/
3. Verify the speed and duplex settings of the installed network adapters. For more information, see Configuring the speed and duplex of an ESX / ESXi host network adapter.
4. Verify that the portgroup and virtual switch are not configured for promiscuous mode. For more information, see Configuring promiscuous mode on a virtual switch or portgroup.
5. Verify the host is not overloaded. Networking relies on available processor resources. If the CPUs on the host are being used at capacity, network performance suffers.
6. Verify the appropriate network driver for the virtual machine based on environmental needs. For more information, see Choosing a network adapter for your virtual machine.