What is a distributed switch in VMware used for?

A distributed switch in VMware is primarily designed to provide centralized management of virtual networking across multiple ESXi hosts within a vSphere environment. This allows network administrators to configure, manage, and monitor networking settings for all connected virtual machines (VMs) and their network interfaces from a single point, rather than needing to configure each virtual switch on individual ESXi hosts separately.

By using a distributed switch, network policies, including security and traffic shaping settings, can be applied in a consistent manner across all VMs that are united under that switch. This not only simplifies management but also enhances the performance of network traffic flow in large, virtualized environments. Furthermore, features like network I/O control and port mirroring become easier to implement, facilitating more efficient network resource allocation and troubleshooting.

This central management capability makes option B the most accurate response regarding the purpose of a distributed switch in VMware.