VMs take advantage of Virtual Networking.  So do ESXi hosts and vCenter.  This allows multiple VMs to share a single network card.

• Virtual Machines must have proper addresses and protocols
• Use Virtual Switches to attach VMs to the physical network, or
• Create isolated networks to use during testing and development
• Provides same flexibility that server virtualization provides

vSphere provides 2 categories of switches

• Standard Virtual Switch (Default): Manages VM networking at the Host level
• Distributed Virtual Switch: Manages networking at the Data Center level

Features Provided

• VLANs
• Traffic Shaping: Restrict inbound and outbound traffic of a group of VMs
• Port Mirroring: Monitor VMs traffic for troubleshooting or intrusion prevention.  Can capture all traffic sent to or from for later inspection
• Quality of Service (QoS) and DSCP:  Used to prioritize network traffic over others. (VOiP traffic over Web)
• NetFlow: Network monitoring tool to determine top talkers on the network as well as other metadata to understand the types of communications that occur.
• CDP and LLDP: Discovery protocols used to identify neighboring physical network switches.  Good for discovery and troubleshooting