For my test lab I use an IBM x3850 M2 model 7141-3RM. Its a 4 socket server, with 4 cores per socket and 96Gb Ram running nested ESXi hosts.

Until recently, I was still running ESXi 5.0 on the physical host, with nested ESXi 5.1 hosts which worked perfectly.

Recently I decided to upgrade the physical host to ESXi 5.1.

Problem: My nested ESXi 5.1 hosts can no longer run 64bit VMs.

Now why is that? The Intel E7330 supports Intel-VT-x w Extended Page Tables (see Intel’s website here) or so they say?!

As mentioned by William Lam (@lamw) on his blog (VirtuallyGhetto)

A quick way to verify whether your CPU truly supports both Intel-VT+EPT or AMD-V+RVI, you can paste the following into a browser:

https://[your-esxi-host-ip-address]/mob/?moid=ha-host&doPath=capability

So, after running this on my host, I got the following result

So that’s a bummer, I cant run ESXi 5.1 on my physical host with nested ESXi hosts running 64 bit VMs.

Note: 32bit VMs run fine.

So, Intel are telling fibs about what this processor can do, but that doesn’t help solve the issue.

Solution: If you have this processor in your test lab and/or have the IBM x3850 M2 model 7141-xxx (or you obtain one as they are a great low cost option for a test lab) run ESXi 5.0 on the physical host, and run ESXi 5.1 nested and you can run 64bit VMs.