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ESXi Config Restore Bug

While I was looking into various ways to restore an ESXi config backup I came across a bug.

If you read VMware’s documentation about how to restore an ESXi config backup (you can find that here) you will see that it is full of references saying the build numbers must match.

The bug is that you can restore an ESXi config backup even if the build numbers don’t match. Which according to the VMware documentation should not be possible.

Even though it is possible to restore an ESXi config backup when the build numbers don’t match, I do not recommend doing this as there has to be a reason why VMware says that the build numbers must match.

In my testing I was able to replicate the bug in ESXi 7 and ESXi 8. I even went all the way back to ESXi 6.7 which had some interesting findings. I didn’t fully test everything in ESXi 6.7 as general support has ended on that version.

Here are my findings and how to replicate the bug.

ESXi Build Number without vCenter

Knowing your ESXi Build Number can be very useful. It’s really easy to do with vCenter. Without vCenter it’s not as straight forward. Here are a few ways to get your build number when you don’t have vCenter.


If you have access to the console of the ESXi host via IPMI or iLO or iDRAC or physical access, you can get your ESXi build number right from there, you don’t even need to login.

Help Menu

You can also get your ESXi build number right from the Help menu in the Web UI.

  • Login to the Web UI of your ESXi host
  • Click on Help > About

You will now get a screen that show you your ESXi build number.

It should look something like this

In this example we know that my ESXi build number is 19482537.


  • Enable SSH on your ESXi Host by right clicking on the host and selecting Services > Enable Secure Shell
  • Login to your ESXi host with SSH
  • Enter the following command vmware -v

You will get an output that looks something like this

VMware ESXi 7.0.3 build-19482537

In this example we know that my ESXi build number is 19482537.

ESXi Config Backup File

You can also get your ESXi build number from an ESXi config backup file, which can be helpful if you want to know which ESXi build number was installed when a backup was taken.

To do this we will need something that can open a tgz archive. I like to use 7-Zip.

Cisco Aironet Won’t Connect to Wireless LAN Controller

I ran into an issue where some older Cisco Aironet APs (Access Points) stopped connecting to a Cisco WLC (Wireless LAN Controller). No config changes had been made and some of the Cisco Aironet APs would connect and some wouldn’t. All of them were the same model, the Cisco Aironet APs were able to ping the Cisco WLC and vice versa.

What happened is the Cisco MIC (Manufacture Installed Certificate) expired and the default setup of a Cisco WLC is to reject any Cisco Aironet AP with an expired MIC.

It looks like this could impacts every Cisco WLC when used with older Cisco Aironet APs that have an expired Cisco MIC. Cisco has a Field Notice about this issue, you can read it here FN63942.

Any Cisco Aironet AP that was manufactured from July 18, 2005 until 2017 will have a Cisco MIC that expires 10 years after the manufacture date. There seems to be no way to replace or renew that Cisco MIC, this will keep being an issue that could randomly show up until 2027 when all of them should be broken.

The reason some of my Cisco Aironet APs worked and some didn’t is because they were manufactured at different times even though they have the same model number.

The fix is super quick we just need to tell the Cisco WLC to ignore expired Cisco MICs.

Cisco UCS Upgrade with Firmware Auto Install

Recently I needed to upgrade a Cisco Unified Computing System (UCS) system and while Cisco does have documentation about it. The process can be scary and could use more screenshots. Here is my step by step guide on how to upgrade a Cisco UCS via the Firmware Auto Install with the Cisco UCS Manager.

Fully planning your Cisco UCS upgrade is very important. There are a lot of things that need to be checked to make sure the upgrade is a success and that everything is compatible. In the past I’ve needed to upgrade my ESXi to as high as they can go based on the VMware and Cisco Compatibility Matrix and then upgrade the Cisco UCS. Then go back and upgrade ESXi again and then upgrade Cisco UCS again.

Quick Cheat Sheet

Fixing Teams needs an update

Recently I’ve ran into an issue with Microsoft Teams where the user sees a blocking message that says “Teams needs an update”. The user needs to action it before they can use Microsoft Teams again. Typically the user can just click on Update Teams which will take them to a download page for Microsoft Teams, they also need to pick the correct version of Microsoft Teams because now there are two of them.

Let’s have some faith in the user and say they do download the correct version, now they need to run the downloaded file and then it will update Microsoft Teams for them and finally they can use Microsoft Teams again.

That whole process isn’t a good user experience and that’s way too many steps. It’s worse if the user is in a rush because let’s say the system with the outdated version of Microsoft Teams is a meeting room computer and they are trying to load Microsoft Teams for their meeting.

There has to be a way to prevent this and a way to reliably solve the Teams needs an update problem. Here’s what I found in this rabbit hole along with the solutions I found.