<div>
If you're running vCenter you would need to upgrade vCenter (including SSO which is now part of PSC, as well as a few more upgrade with vCenter). &nbsp;Otherwise you can run a mixed cluster with 5.x and 6
</div>


If you're running vCenter you would need to upgrade vCenter (including SSO which is now part of PSC, as well as a few more upgrade with vCenter).  Otherwise you can run a mixed cluster with 5.x and 6

<div>
If you're referring to the free version of ESXi, you can still download 5.1 from here: <a href="https://my.vmware.com/group/vmware/evalcenter?p=free-esxi5" rel="ugc nofollow">https://my.vmware.com/group/vmware/evalcenter?p=free-esxi5</a>
</div>


If you're referring to the free version of ESXi, you can still download 5.1 from here: https://my.vmware.com/group/vmware/evalcenter?p=free-esxi5 [https://my.vmware.com/group/vmware/evalcenter?p=free-esxi5]

<div>
Andrew,<br />
So if we upgrade the vcenter to version 6 then we could add the new host with esxi 6 and then leave the others at ESXi 5.1?
</div>


Andrew,
So if we upgrade the vcenter to version 6 then we could add the new host with esxi 6 and then leave the others at ESXi 5.1?

<div>
<blockquote>
Andrew,<br />
So if we upgrade the vcenter to version 6 then we could add the new host with esxi 6 and then leave the others at ESXi 5.1?
</blockquote>
<br />
Yes
</div>


> Andrew,
> So if we upgrade the vcenter to version 6 then we could add the new host with esxi 6 and then leave the others at ESXi 5.1?


Yes

<div>
esxi 6 running with esxi 5.1
</div>


<div>
<div class="content wysiwyg-content">
We have 4 host running ESXi 5.1 and we need to add another host and we can only get ESXi 6 now. Would it be ok to run the 1 host with ESXi 6 in the cluster with the 4 others with ESXi 5.1 or should we just upgrade all of them to ESXi 6?
</div>
</div>


We have 4 host running ESXi 5.1 and we need to add another host and we can only get ESXi 6 now. Would it be ok to run the 1 host with ESXi 6 in the cluster with the 4 others with ESXi 5.1 or should we just upgrade all of them to ESXi 6?

Can we run ESXi 5.1 with ESXi 6?

VMware, a software company founded in 1998,  was one of the first commercially successful companies to offer x86 virtualization. The storage company EMC purchased VMware in 1994. Dell Technologies acquired EMC in 2016. VMware’s parent company is now Dell Technologies.

VMware has many software products that run on desktops, Microsoft Windows, Linux, and macOS, which allows the virtualizing of the x86 architecture.  Its enterprise software hypervisor for servers, VMware vSphere Hypervisor (ESXi), is a bare-metal hypervisor that runs directly on the server hardware and does not require an additional underlying operating system.