Here are some instructions to help you understand how to upgrade Infoblox to the current latest version

First step is to log into Infoblox with an Admin account and click on the Grid Tab, then Upgrade and now click the Upload button, browse to the Infoblox image you downloaded from (http://support.infoblox.com) and click OK to begin the upload process.

You should now see the Upload button gray out and in the black bar in the middle of the screen you will see Grid Upgrade Status with a % and the status message of Upload in progress as well as what image file is uploading.  All kinds of good information.

Once the upload is completed you will be presented with a screen like the one shown below.  The Distribute button is now available to  be selected, this will distribute the Uploaded image to the rest of the members.  This only stages the image, it doesn't do any installation.  This takes roughly 20-30 minutes once you click the Distribute button.

Once you click the Distribute button, Infoblox wants to make sure you are aware that by distributing this new image it requires removing your backup copy (in the screen below, it needs to remove 7.2.6-316673 to stage 7.3.6-335725 to upgrade 7.3.4-322642). In short, Infoblox can only have two versions.  The one its running and either the one it is going to or the one it could revert back to. Anyhow, click Yes to continue.

Now it begins to copy the image from the Grid Master to the members in your Grid. Again, this is only staging the image, it is not installing anything.

Sometimes after the image is distributed you have to click the Test button to make sure everything is good but in this case Infoblox did the test automatically so I didn't have to click the Test button.  Now you are presented with the almighty Upgrade button.  When you click the Upgrade button it will begin upgrading the Infoblox environment starting with the Grid Master.

Upon clicking the Upgrade button you will be presented with a confirmation message like the one below. You must click Yes to continue.

Here is a snapshot of during the upgrade process where the Grid Master has been updated and the rest of the members are being upgraded.

When everything is done upgrading you will get screens like the two below.

I like to verify DHCP is working after an upgrade so I click on the Data Management tab and then DHCP - Leases - Lease History and click Refresh to see new timestamps for leases handed out.

You have completed your upgrade of Infoblox. 

Just upgraded to NIOS 8.1.0 and got some weird results.  Something new to me is the Upgrade Status:

Quote

1 of 1 node has completed upgrade, in revert window

WHY?
 
NIOS now includes a built-in revert window, where the entire Grid can be reverted to the old NIOS version without any changes to the database. This is a disaster recovery mechanism. The revert window ensures that all protocol services and Grid communication is working fine in the new NIOS release.  Administrative tasks are restricted in the revert window.
 
 
FIX?
 
To gain administrative access to the Grid immediately after an upgrade, run the following command from the Grid Master:

Infoblox > set grid_upgrade forced_end

"set grid_upgrade forced_end" is a Grid Master CLI command, that can be used during or at the end of a running upgrade. It can be also used in the middle of an upgrade to change the revert window of the members that have not been upgraded yet.  Executing it after all members are upgraded and before the revert-timer expires, forces the revert timer to expire, thus allowing admin changes to take place. 
 
NOTE:  If executing this command before members have completed their upgrade, will force the upgrade to end, and any members that are not upgraded will reboot and perform a code-sync to the new version. Those appliances will be offline during their sync to the new version. If any of the members are running a different NIOS version than the Grid , please do not use this command.  We recommend you to contact Infoblox technical support for further assistance.