Consider these best practices when you configure your network.

Separate network services from one another to achieve greater security and better performance.

Put a set of virtual machines on a separate physical NIC. This separation allows for a portion of the total networking workload to be shared evenly across multiple CPUs. The isolated virtual machines can then better serve traffic from a Web client, for example

Keep the vMotion connection on a separate network devoted to vMotion. When migration with vMotion occurs, the contents of the guest operating system’s memory is transmitted over the network. You can do this either by using VLANs to segment a single physical network or by using separate physical networks (the latter is preferable).

When using passthrough devices with a Linux kernel version 2.6.20 or earlier, avoid MSI and MSI-X modes because these modes have significant performance impact.

To physically separate network services and to dedicate a particular set of NICs to a specific network service, create a vSphere standard switch or vSphere distributed switch for each service. If this is not possible, separate network services on a single switch by attaching them to port groups with different VLAN IDs. In either case, confirm with your network administrator that the networks or VLANs you choose are isolated in the rest of your environment and that no routers connect them.

You can add and remove network adapters from a standard or distributed switch without affecting the virtual machines or the network service that is running behind that switch. If you remove all the running hardware, the virtual machines can still communicate among themselves. If you leave one network adapter intact, all the virtual machines can still connect with the physical network.

To protect your most sensitive virtual machines, deploy firewalls in virtual machines that route between virtual networks with uplinks to physical networks and pure virtual networks with no uplinks.

For best performance, use vmxnet3 virtual NICs.

Every physical network adapter connected to the same vSphere standard switch or vSphere distributed switch should also be connected to the same physical network.

Configure all VMkernel network adapters to the same MTU. When several VMkernel network adapters are connected to vSphere distributed switches but have different MTUs configured, you might experience network connectivity problems.