Symptoms:

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

VMware ESXi 4.0.x Embedded
VMware ESXi 3.5.x Embedded
VMware ESX Server 3.5.x
VMware vCenter Server 5.1.x
VMware vSphere ESXi 6.5
VMware ESX 4.0.x
VMware vCenter Server 5.0.x
VMware ESX Server 3.0.x
VMware VirtualCenter 2.5.x
VMware vCenter Server 4.0.x
VMware ESXi 3.5.x Installable
VMware vCenter Server 5.5.x
VMware ESXi 4.0.x Installable
VMware VirtualCenter 2.0.x
VMware vSphere ESXi 5.1
VMware vSphere ESXi 5.5
VMware ESXi 4.1.x Installable
VMware vSphere ESXi 6.7
VMware vSphere ESXi 6.0
VMware ESX 4.1.x
VMware ESXi 4.1.x Embedded
VMware vSphere ESXi 5.0
VMware vCenter Server 4.1.x

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

Validate that each troubleshooting step below is true for your 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 (1003947) and Overview of VMware Tools (340).
    
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 (1004088).
    
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 (1004089).
    
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 (1004099).
    
5. Verify the integrity of the physical network adapters. For more information, see Verifying the integrity of the physical network adapter (1003686).
    
6. Verify that your host is not overloaded. Networking relies on available processor resources. If the CPUs on the host are being used at capacity, network performance suffers.
    
7. Verify that you have chosen the appropriate network driver for your virtual machine based on your needs. For more information, see Choosing a network adapter for your virtual machine (1001805).
    

If your problem still exists after trying the steps in this article:

1. Gather the VMware Support Script Data. For more information, see Collecting diagnostic information for the vSphere Client or VMware Infrastructure Client (1003687).
2. File a support request with VMware Technical Support and note this KB Article ID (1004087) in the problem description. For more information, see How to Submit a Support Request.

For related information, see:

• Performance Tuning Best Practices for ESX Server 3
• Networking Performance in VMware ESX Server 3.5

Choosing a network adapter for your virtual machine
Verifying the integrity of the physical network adapter on an ESX/ESXi host
Collecting diagnostic information for the vSphere Client or VMware Infrastructure Client
Collecting diagnostic information in a VMware Virtual Infrastructure Environment
Verifying a VMware Tools build version
NIC teaming in ESXi and ESX
Configuring the speed and duplex of an ESXi or ESX host network adapter
Configuring promiscuous mode on a virtual switch or portgroup
vSphere 環境でのネットワークパフォーマンスの問題のトラブルシューティング
排除 vSphere 环境中的网络性能问题
Overview of VMware Tools