Choosing a network adapter for your virtual machine
Details
The virtual machine configuration window for network connection allows you to specify a network and a network adapter. The network adapter choices that are available depend on the virtual machine version number and the guest operating system running on the virtual machine.
The Choose Networks window makes available only those network adapters that make sense for the virtual machine you are creating.
Solution
Available Network Adapters
The following network adapters might 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.
I f 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.