Lockdown mode is a critical security feature for an ESXi host. When enabled, it restricts management access to the host, forcing all operations to be performed through vCenter Server. This prevents users from logging in directly to the host via the Direct Console User Interface (DCUI) or the ESXi Shell and SSH services. By centralizing control and eliminating direct access points, lockdown mode significantly enhances the security posture of the host, protecting it from unauthorized local or remote management activities.

A. Improves network performance.

Lockdown mode is a security configuration and has no direct function related to the host's networking stack or its performance.

C. Increases CPU and memory resources available to virtual machines (VMs).

This feature does not affect the hypervisor's resource scheduler or the allocation of physical CPU and memory resources to virtual machines.

D. Simplifies the management of virtual machines.

While centralizing management in vCenter is a best practice, lockdown mode's primary purpose is security, not simplification. It can complicate direct troubleshooting.

1. VMware vSphere 6.0 Documentation

vSphere Security Guide

PDF.

Reference: Chapter 13

"ESXi Security

" Section: "ESXi Lockdown Mode

" Page 121.

Quote: "You can enable lockdown mode for an ESXi host. When you enable lockdown mode

no users other than vpxuser have authentication permissions

nor can they perform operations against the host directly. Lockdown mode forces all operations to be performed through vCenter Server." This directly supports that the feature restricts access to enhance security.

2. VMware Knowledge Base (KB) Article 1008077.

Reference: "ESXi Lockdown Mode" (1008077)

Purpose section.

Quote: "This article provides information about ESXi Lockdown Mode. Lockdown mode increases the security of an ESXi host by limiting management of the host to a vCenter Server." This confirms the security benefit by restricting management.