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Is the vCenter Server Unique ID still important today?

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When I was a customer back in the day, one of my operational checklist items for deploying a vCenter Server was to configure the vCenter Server ID and ensure that it was unique from other vCenter Servers within my environment.


The vCenter Server ID is a value between 0-63 that is randomly generated by default, but it can updated by a user after the vCenter Server has been deployed.

Why should you care about the vCenter Server ID? vCenter Server uses this ID to generate Virtual Machine MAC Addresses and if two vCenter Servers have the same ID, it can potentially generate duplicate VM MAC Addresses as explained in this VMware KB 1024025.

With this background in mind, is having a unique vCenter Server ID still relavent and applicable today in 2022?

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Does vCenter Server recycle VM MAC Addresses after Cross vCenter vMotion?

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I recently received a question from a customer who was concerned that after a VM has been migrated from one vCenter Server to another using Cross vCenter vMotion, that the original source VM MAC Address could potentially be recycled and re-used at a later point. Back in 2015, I actually wrote about this very topic and the concerns around VM MAC Address duplication after a Cross vCenter vMotion, which I highly encourage folks to check out if you have not seen this article already.

While re-reading the article, I realized that the article had primarily focused on vCenter Servers that were in Linked Mode or under the same vSphere Single Sign-On (SSO) domain and although I did mention the Cross vCenter vMotion across across different vSphere SSO domains scenario, it looks like the details were a tad bit light.

To quickly summarize, when a VM is migrated from a source vCenter Server to the designation vCenter Server, the VM's MAC Address is added to a MAC Address "block list" on the source vCenter Server. This ensures that the VM MAC Address will not be reallocated by the source vCenter Server which would cause a network conflict. This has been the default behavior since vSphere 6.0 and no additional configuration change is required by customers.

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Quick Tip - Crucial NVMe SSD not recognized by ESXi 6.7 & 7.0

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If you own or have recently purchased Crucial NVMe SSD such as CT1000P1SSD8 (1TB M.2 NVMe SSD) or CT500P1SSD8 (500GB M.2 NVMe SSD), please be aware that these devices may no be recognized by ESXi after upgrading to the latest release. Thanks to Pete Lindley, (OCTO for End-User Computing), who reached out last week regarding the observation as well as a workaround for the problem. This was also quite timely as I recently purchased a Crucial M.2 NVMe SSD and would have also ran into this problem.

It turns out these Crucial devices were working fine while running on ESXi 6.5 Update 2 but was no longer recognized in latest release of ESXi 6.7 Update 2. It is unclear whether support for these SSDs were removed intentionally or unintentionally, but in either case, these devices are not officially on VMware's Hardware Compatibility List (HCL).

UPDATE (07/29/20) - Over the past few months, I have had a number of folks share feedback that using the trick mentioned below for ESXi 7.0, they have had success of ESXi detecting their NVMe SSD. I wanted to share some of the model and/or vendors that folks have reported success with. I will keep this list updated, so feel free to leave a comment below.

UPDATE (06/13/20) - Thanks to reader Dave, it looks like this trick also works with ESXi 7.0 but the filename has changed. Simply copy nvme.v00 VIB from the ESXi 6.5 Update 2 and replace it on ESXi 7.0 system (either live under /bootbank or part of the installer) but rename the file to nvme_pci.v00 which is the new filename for NVMe driver.

UPDATE (05/23/19) - After speaking with a few folks who took a closer look, the issue is due to the fact that we added support for NVMe 1.3 spec in latest ESXi 6.7 Update 2 release, but because these are "consumer" devices, they did not conform to the latest specification and hence the driver is unable to claim the device. This is another good reminder when using components not on VMware HCL, this is always a risk from a home lab perspective. In general, I know Samsung and Intel NVMe SSD usually works quite well without issues but always good to do some research. I think Engineering is looking to see if there are other workarounds for the future, but for now, you can use the workaround below.

The easy workaround that Pete found was to simply replace the NVMe driver from ESXi 6.7 Update 2 (1.2.2.27-1vmw.670.2.48.13006603) with one found in ESXi 6.5 Update 2 (1.2.1.34-1vmw.650.2.50.8294253). To so do, simply copy nvme.v00 to /bootbank from either an existing ESXi 6.5 Update 2 system or directly from the ISO. Please note, any future updates or patches to the ESXi host will most likely override the updated driver.