This post is from My blog http://www.vmwarearena.com/2013/07/esxi-vsphere-client-error-you-do-not.html
This post is for the administrators who are more familiar with managing ESX hosts and new to ESXi hosts. There are many environment with lot of ESX hosts and ESXi hosts are introduced to the environment after the vSphere 5. only ESXi will be available post vSphere 5 and ESX is discontinued. So there are many administrators who are new to ESXi management. When you tried to connect to your ESXi host directly via vSphere client as like connecting to ESX server. You may face the error message " The vSphere client could not connect to "x.x.x.x". You don't have permission to login to the server"
Don't be panic and don't try to restart your management services as all administrators do when they are not able to connect to the host via vSphere client.This above error is because of the "ESXi Lockdown Mode is Enabled" in your ESXi host.
When ESXi Lockdown mode is enabled, it will not allow any other user other than vpxuser have authentication permission and no other users can perform operations against the host directly. Lockdown Mode forces all operations on the host to be performed through vCenter server. Root user account can be used to login to DCUI when ESXi lockdown mode is enabled.
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