ESX Configuration Guide

Port Groups

Port groups aggregate multiple ports under a common configuration and provide a stable anchor point for virtual machines connecting to labeled networks.

Each port group is identified by a network label, which is unique to the current host. Network labels are used to make virtual machine configuration portable across hosts. All port groups in a datacenter that are physically connected to the same network (in the sense that each can receive broadcasts from the others) are given the same label. Conversely, if two port groups cannot receive broadcasts from each other, they have distinct labels.

A VLAN ID, which restricts port group traffic to a logical Ethernet segment within the physical network, is optional. For a port group to reach port groups located on other VLANs, the VLAN ID must be set to 4095. If you use VLAN IDs, you must change the port group labels and VLAN IDs together so that the labels properly represent connectivity.

Port Group Configuration for Virtual Machines

You can add or modify a virtual machine port group from the vSphere Client.

The vSphere Client Add Network wizard guides you through the tasks to create a virtual network to which virtual machines can connect, including creating a vSwitch and configuring settings for a network label.

When you set up virtual machine networks, consider whether you want to migrate the virtual machines in the network between hosts. If so, be sure that both hosts are in the same broadcast domain—that is, the same Layer 2 subnet.

ESX does not support virtual machine migration between hosts in different broadcast domains because the migrated virtual machine might require systems and resources that it would no longer have access to in the new network. Even if your network configuration is set up as a high-availability environment or includes intelligent switches that can resolve the virtual machine’s needs across different networks, you might experience lag times as the Address Resolution Protocol (ARP) table updates and resumes network traffic for the virtual machines.

Virtual machines reach physical networks through uplink adapters. A vSwitch can transfer data to external networks only when one or more network adapters are attached to it. When two or more adapters are attached to a single vSwitch, they are transparently teamed.