Installing a driver in an existing VMware vSphere 4.1 ESX/ESXi host

We recently purchased some new "Intel Eth QP Ser Adapter T4" cards for our existing VMware ESX 4.1 hosts. The card has four ports, each capable of transmitting one Gbps each.
Unfortunately, the driver for this card isn’t in the default set installed with VMware vSphere. Like all things VMware, getting these to work in an existing host is not the easiest of things. During ESX installation, a big glaring warning message is displayed: “If you choose to not install additional drivers at this time, you will not be able to do so later.” Well, that’s not exactly true. To work around this, just follow the instructions below.

1. Verify that the card is supported by the VMware HCL.
2. Download the driver from VMware’s Driver CD Repository.
3. Put your ESX/ESXi host into maintenance mode.

At this point, you can install additional drivers one of two ways: via the vSphere CLI, where you run the files from your own workstation, or via the esxupdate command on the ESX host itself. I personally prefer to do it via the vSphere CLI.

1. If you haven’t already installed the vSphere CLI, you can get it at VMware.
2. Burn the downloaded ISO to a CD and leave it inserted in your drive.
3. Open a command prompt at “C:\Program Files (x86)\VMware\VMware vSphere CLI\bin” (assuming you are using an x64 flavor of Windows).
4. Use the vihostupdate Perl script as shown: vihostupdate.pl –server <IP Address of host> -username root –install –bundle <path to offline bundle> The “path to offline bundle” is much like what was used in the other option, but it just looks at your local drive. An example would be “D:\offline-bundle\driver.zip”.

vihostupdate.pl --server 192.168.123.10 --username root  --install --bundle D:\offline-bundle\driver.zip

Source : http://4sysops.com