How to update a network driver in ESXi 4.1
Download the Driver CD for the bnx2 driver from the VMware site for the specific ESXi version/driver and use winrar to extract the .iso. This gives you access to the bnx2 driver that is in the offline bundle. Next step is to upload the specific .zip file to a datastore on the esxi host as this allows the file to be used from tech support mode. Enable local or remote tech support mode and run the following command:
esxupdate --bundle=/vmfs/volumes/<datastore name>/<folder in datastore>/bnx2.zip update
Replace the <datastore name> and <folder in datastore> as needed.
Also remember that there is a readme in the docs foler when you extract the .iso.