Registered virtual machines exceed limit on host

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

You receive an event message when the number of virtual machines registered on the host exceeds their limit.

This occurs when clients register more virtual machines on an ESXi host than the host can support.

Impact

If the limit is exceeded, the management agent is at risk of running out of system resources. Consequently, VMware vCenter Server might stop managing the corresponding ESXi host.

Environment

VMware vCenter Server 5.1.x
VMware vSphere ESXi 5.1

Resolution

To ensure management functionality, restrict the number of registered virtual machines to the limit indicated by the vim.host.capability.maxRegisteredVMs property of the ESXi host.

To lower the value of maximum number of allowed registered virtual machines:

1. Edit the VMkernel.Boot.maxRegisteredVMs variable by selecting the host in vCenter Server.
2. Open the Configuration tab and select Advanced Options in the Software box.
3. Expand the VMkernel option and click Boot.
4. Alter the value in the text box to the right of the VMkernel.Boot.maxRegisteredVMs variable.
   

The value is 0 by default and requires a reboot to activate. Having the value set at 0 makes the host determine the value dynamically by amount of memory on host machine. Entering a different number overrides the value.