In VMware vSphere 8.0.2 and later, the default link speed for the vmxnet3 virtual network adapter is 10 Gbps. However, some guest operating systems or applications may not fully utilize this speed or may misinterpret it, causing suboptimal performance. To mitigate this, VMware allows administrators to configure the vmxnet3 adapter’s link speed up to 65 Gbps.
🛠️ Methods to Modify vmxnet3 Link Speed
1. Using the vSphere Client
- Locate the VM: In the vSphere Client, navigate to the desired virtual machine.
- Power Off: Shut down the VM to allow configuration changes.
- Edit Settings: Right-click the VM and select Edit Settings.
- Access Advanced Options: Go to VM Options → Advanced → Edit Configuration.
- Add Parameter:
- Name:
ethernetX.linkspeed(e.g.,ethernet0.linkspeed) - Value: Desired speed in Mbps (e.g.,
65000)
- Name:
- Save Changes: Click OK to apply the settings.
2. Editing the VM’s Configuration File (.vmx) via SSH
- Power Off the VM
- Access ESXi Host: SSH into the ESXi host where the VM resides.
- Navigate to the VM Directory:
cd /vmfs/volumes/<DATASTORE>/<VM_FOLDER> - Edit the .vmx File:
vi <VM_NAME>.vmx - Add Link Speed Parameter:
ethernet0.linkspeed = "65000" - Save and Exit: Write and save the changes.
⚠️ Important Considerations
- Supported Speeds: Valid link speed values range from
10000Mbps to65000Mbps. - Default Behavior: Values outside this range default to
10000Mbps. - Physical Limitations: Changing the virtual adapter’s link speed does not impact the physical NIC capacity.
- Purpose: Intended to resolve guest OS or application misinterpretation of the default 10 Gbps speed.
For complete technical documentation, please refer to the official Broadcom KB article:
How to change the vmxnet3 link speed of a VM
.
By tailoring the vmxnet3 adapter’s link speed, administrators can optimize virtual machine network performance and ensure compatibility and efficiency across diverse workloads.