VMware vSphere

Available Network Adapters

The following network adapters may be available for your virtual machine, depending on the factors discussed above:

• Vlance - An emulated version of the AMD 79C970 PCnet32 LANCE  NIC, an older 10 Mbps NIC with drivers available in most 32bit guest  operating systems except Windows Vista and later. A virtual machine  configured with this network adapter can use its network immediately.
  

• VMXNET - The VMXNET virtual network adapter has no physical  counterpart. VMXNET is optimized for performance in a virtual machine.  Because operating system vendors do not provide built-in drivers for  this card, you must install VMware Tools to have a driver for the VMXNET  network adapter available.
  

• Flexible - The Flexible network adapter identifies itself as a  Vlance adapter when a virtual machine boots, but initializes itself and  functions as either a Vlance or a VMXNET adapter, depending on which  driver initializes it. With VMware Tools installed, the VMXNET driver  changes the Vlance adapter to the higher performance VMXNET adapter.
  

• E1000 - An emulated version of the Intel 82545EM Gigabit  Ethernet NIC, with drivers available in most newer guest operating  systems, including Windows XP and later and Linux versions 2.4.19 and  later.
  

• VMXNET 2 (Enhanced) - The VMXNET 2 adapter is based on the  VMXNET adapter but provides some high-performance features commonly used  on modern networks, such as jumbo frames and hardware offloads. This  virtual network adapter is available only for some guest operating  systems on ESX/ESXi 3.5 and later.
  VMXNET 2 is supported only for a limited set of guest operating systems: 
  • 32 and 64bit versions of Microsoft Windows 2003 (Enterprise and  Datacenter Editions). You can use enhanced VMXNET adapters with other  versions of the Microsoft Windows 2003 operating system, but a  workaround is required to enable the option in VMware Infrastructure  (VI) Client or vSphere Client. See Enabling enhanced vmxnet adapters for Microsoft Windows Server 2003 (1007195) if Enhanced VMXNET is not offered as an option.
    
  • 32bit version of Microsoft Windows XP Professional
    
  • 32 and 64bit versions of Red Hat Enterprise Linux 5.0
    
  • 32 and 64bit versions of SUSE Linux Enterprise Server 10
    
  • 64bit versions of Red Hat Enterprise Linux 4.0
    
  • 64bit versions of Ubuntu Linux
    

• VMXNET 3 - The VMXNET 3 adapter is the next generation of a  paravirtualized NIC designed for performance, and is not related to  VMXNET or VMXNET 2. It offers all the features available in VMXNET 2,  and adds several new features like multiqueue support (also known as  Receive Side Scaling in Windows), IPv6 offloads, and MSI/MSI-X interrupt  delivery.
  VMXNET 3 is supported only for virtual machines version 7 and later, with a limited set of guest operating systems: 
  • 32 and 64bit versions of Microsoft Windows XP and later
    
  • 32 and 64bit versions of Red Hat Enterprise Linux 5.0 and later
    
  • 32 and 64bit versions of SUSE Linux Enterprise Server 10 and later
    
  • 32 and 64bit versions of Asianux 3 and later
    
  • 32 and 64bit versions of Debian 4/Ubuntu 7.04 and later
    
  • 32/64bit versions of Sun Solaris 10 U4 and later
    

Adapter Caveats

This section discusses some potential problems you might have.

• Migrating virtual machines that use enhanced vmxnet
  VMXNET 2 is new with ESX 3.5 virtual machines configured to have VMXNET  2 adapters cannot migrate to earlier ESX hosts, even though virtual  machines can usually migrate freely between ESX 3.0 and ESX 3.0.x.
  If you must migrate a virtual machine between later and earlier hosts, do not choose VMXNET 2.
  

• Upgrading from ESX 2.x to ESX 3.x
  When a  virtual hardware upgrade operation transforms a virtual machine created  on an ESX 2.x host to an ESX 3.x host, Vlance adapters are automatically  upgraded to Flexible. In contrast, VMXNET adapters are not upgraded  automatically because most or all Linux guest operating system versions  do not reliably preserve network settings when a network adapter is  replaced. Because the guest operating system thinks a Flexible adapter  is still Vlance, it retains the settings in that case. If the upgrade  replace a VMXNET adapter with a Flexible adapter, the guest operating  system erroneously discards the settings.
  After the  virtual hardware upgrade, the network adapter is still VMXNET, without  the fallback compatibility of the Flexible adapter. Just as on the  original earlier host, if VMware Tools is uninstalled on the virtual  machine, it cannot access its network adapters.
  

• Adding virtual disks
  Adding an existing  earlier (ESX 2.x) virtual disk to an ESX 3.x virtual machine results in a  de-facto downgrade of that virtual machine to ESX 2.x. If you are using  ESX 3.x features, such as enhanced VMXNET or Flexible network adapters,  the virtual machine becomes inconsistent. When you add an existing ESX  2.x virtual disk to an ESX 3.x machine, immediately use the Upgrade Virtual Hardware command to restore the virtual machine to the ESX 3 version. This  problem does not arise when you add earlier virtual disks to an ESX/ESXi  4.0 virtual machine.
  Note: Executing Upgrade Virtual Hardware changes the ESX 2 virtual disk so that it is no longer usable on an ESX  2 virtual machine. Consider making a copy of the disk before you  upgrade one of the two copies to ESX 3 format.
  

• Problems with VMware FT
  The new vmxnet3 virtual NIC is not compatible with VMware FT, see: http://blog.scottlowe.org/2009/07/05/another-reason-not-to-use-pvscsi-or-vmxnet3/
  

Change network adapter

From GUI is not possible change the type of an existing network adapter. The choice exist only for new adapter.
For change the type manually by editing the vmx file see:
http://malaysiavm.com/blog/how-to-change-virtual-machine-network-adapter-manually/

Performance difference

http://www.vmware.com/files/pdf/perf_comparison_virtual_network_devices_wp.pdf
http://www.vmware.com/pdf/vsp_4_vmxnet3_perf.pdf
http://blog.vmpros.nl/2009/09/22/vmware-performance-evaluation-of-vmxnet3-virtual-network-device/

Reference

Choosing a network adapter for your virtual machine - http://kb.vmware.com/kb/1001805
http://blogs.vmware.com/networking/2009/06/what-vnic-choosing-an-adapter-for-your-vm.html
vmxnet3 - features and use information - tips and tricks
Which NIC for Windows 2008?  E1000 or VMXNET 3?