Here, I would like to share how to change virtual machine virtual network adapter manually. In fact, you may know you can add a new virtual adapter and choose the adapter type from drop down menu.

Here you go:

1. Login to VMware ESX server
2. Type vmware-cmd -l and look for virtual machine (vmx = vm config file) which require change virtual network adapter
3. You may check VMware KB Article: 1001805 for available network adapters details.

# 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.

4. Edit Virtual Machine vmx file and choose virtual network adapter as show below:

Flexible
Nothing have to add into vmx file.

VMXNET 3
ethernetX.virtualDev = “vmxnet3″

Note: ethernetX = number of ethernet card.

5. Save the VMX file and power on your virtual machine.
6. Power on your virtual machine using virtual center or type # vmware-cmd your_virtualmachine.vmx start

Enjoy!