ESXi host vmnics report 10Gbps link speed instead of expected 20Gbps or higher

Products

• VMware vSphere ESXi

Issue/Introduction

An ESXi host shows physical network adapters operating at 10Gbps (10000 Mbps) despite the adapter and environment being designed for 20Gbps or higher throughput. This often occurs in blade server deployments where high-bandwidth Converged Network Adapters (CNAs) are utilized.

Symptoms:

• esxcli network nic list shows "Speed" as 10000.
  
  
• vSphere Client reports "10 Gbps" under Physical Adapters.
  
  
• Speed selection is restricted to 1G/10G/Auto.
  
  
• The adapter is a Broadcom BCM57414 (bnxtnet driver).

Environment

VMware ESXi 6.x / 7.x / 8.x

 

Cause

This issue typically stems from one of several factors related to hardware negotiation or software compatibility. The most common root causes include:

1. Media Auto-Negotiation Failure: If the "Media Auto Detect" setting is disabled within the server BIOS, or if the driver fails to correctly parse the 20G (or higher) link profile, the system may fail to initialize at the intended speed. When the driver cannot verify high-speed capability during media training, it defaults to a suppressed speed advertisement of 10G within the ESXi stack.
    
2. Version Incompatibility: The current driver and firmware versions may be outdated, leading to a non-compliant state within the VMware environment and preventing optimal performance.

Resolution

1. BIOS/UEFI Configuration

If hardware-level negotiation failure is suspected, verify that "Media Auto Detect" is active. The following steps are generalized for modern server platforms (e.g., HPE ProLiant):

1. Access System Utilities: Reboot the ESXi host and enter the System Utilities menu (typically via F9).
   
   
2. Navigate to Adapter Settings: Select System Configuration > BIOS/Platform Configuration (RBSU) > Network Options.
   
   
3. Configure Device: Select the specific network adapter, then enter the Device Configuration Menu.
   
   
4. Enable Media Auto-Detect: Ensure Media Auto Detect is set to Enabled.
   
   
5. Commit Changes: Save the settings and exit. This allows the adapter to dynamically negotiate 20G or higher link profiles.

2. Driver and Firmware Compliance Verification

Ensure the software stack is compliant with the VMware Compatibility Guide (VCG). Outdated or mismatched drivers can result in failed media training for high-speed profiles.

To check versions: esxcli network nic get -n vmnicX

Note: Replace vmnicX with your specific iSCSI vmnic IDs.

Refer to the following KB article for FAQ: Recommendation for drivers/firmware for ESXi hosts

3:  Command Line Override

If the UI remains restricted, use the ESXCLI to force the interface speed.

Note: Ensure the physical switch port is also configured for 20G Fixed or Auto-Negotiation to match.

1. 1. Log in to the ESXi host via SSH.
      
      
   2. Run the following command to set the speed:  esxcli network nic set-n vmnicX -S 20000 -D full


   3. Verify the change:  esxcli network nic get -n vmnicX

 

Additional Information

It is generally recommended to install the latest firmware and driver package that is applicable to your specific server.

For more details on specific hardware limitations regarding 20Gbps or higher throughput, refer to your hardware vendor's documentation.

NOTE:  In the context of this article, the word "vendor" means:
a) The server vendor, if the server was purchased with the device (network adapter and/or HBA) installed; or
b) The vendor of the device, if the device (network adapter and/or HBA) was purchased separately.