What to Do When VMware VMNICs Go Down After an ESXi Upgrade

If you have recently upgraded your VMware ESXi system, you may be experiencing problems with VMNICs (virtual machine network interface cards) not working. This issue can occur when the new version of the hypervisor is incompatible with the existing hardware. Fortunately, there are ways to troubleshoot these issues and get your VMNICs up and running again. In this blog post, we will discuss how to troubleshoot VMware VMNICs that are not working after an ESXi upgrade.

Troubleshooting Steps for VMware VMNICs Not Working After an ESXi Upgrade

1. Check the compatibility of your hardware: The first step in troubleshooting this issue is to check whether or not your system’s hardware is compatible with the new version of VMware ESXi that you have installed. You can do this by visiting the official VMware Compatibility Guide website and searching for your specific model number. If you find that your system’s hardware is not supported by the new version of ESXi 8.0, then you will need to reinstall a compatible version in order to get your VMNICs working again.
2. Check for driver updates: Another possible cause of this issue could be outdated drivers on your system’s hardware components. To check if any driver updates are available, visit the manufacturer’s website and download them directly from there. Once they have been downloaded, install them on your system and restart it to see if this fixes the issue with your VMNICs not working after an ESXi 8.0 upgrade.
3. Resetting Network Settings: If neither of these steps has fixed the problem, then try resetting all network settings on both your physical server as well as within VMware itself by going into “Network Adapters” in vCenter Server and selecting “Reset All Settings” from the drop-down menu at the top right-hand corner of the page. This should restore all network connectivity within VMware and hopefully resolve any issues with your VMNICs not working after an ESXi upgrade.

Troubleshooting VMNICs in VMware ESXi 8.0

If the peer physical switch of a VMNIC does not support Media Auto Detect, or Media Auto Detect is disabled, and the VMNIC link is set down and then up, the link remains down after upgrade to or installation of VMware ESXi 8.0.

Workaround: Use either of these 2 options:

1. Enable the option media-auto-detect in the BIOS settings by navigating to System Setup Main Menu, usually by pressing F2 or opening a virtual console, and then Device Settings > <specific broadcom NIC> > Device Configuration Menu > Media Auto Detect. Reboot the host.
2. Alternatively, use an ESXCLI command similar to: esxcli network nic set -S <your speed> -D full -n <your nic>. With this option, you also set a fixed speed to the link, and it does not require a reboot.

Final Tips VMware VMNICs

VMware VMNICs can go down after an upgrade due to incompatibility between versions or outdated drivers on physical server components. However, if you follow these simple steps then you should be able to troubleshoot this issue quickly without having to reinstall a different version of ESXi or manually update drivers on each component individually—saving you time and effort in getting everything back up and running again! With these tips in mind, engineers should now have a clear idea about how they can fix their VMWare VMNICS when they go down after an upgrade!