Setting this object to noUpgrade(2) results in no
action. When set to upgrade(1), the switch will attempt
to download a firmware upgrade image from the server
whose address is given by upgradeTFTPServerAddress.
The image is found in the file whose name is given by
sibuFlashTFTPLoadFilename. Both
sibuFlashTFTPServerAddress and
sibuFlashTFTPLoadFilename must be non-empty for the
upgrade to proceed.
This object always returns noUpgrade(2) when read.