Configure iDrac6 (Remote Access Controller 6) on ESXi Hosts

Right Click on ESXi1 and Enter Maintenance Mode. Yes to move VMs and OK.
Drag to Move the ESXi1 from VMware 5.1 Cluster to Maintenance Cluster
Open a KVM to Press Ctrl + E to enter to setup
Select LAN Parameters
Enable VLAN and Set VLAN ID to 255
Click Domain Name and input vmlab.local
Save changes and Exit
Reboot the host and verify with the ping test to the remote console IP works properly.
Open IE, and type console IP and click Continue to this website (not recommended)
Type username and password to get access to remote access controller
Verify it accesses properly

Configure Dell OpenManage Integration plug-ins on vCenter environment

On vSphere Client, access to vc5 and go to Home>Load Dell Management Center
Yes to continue
Connection Profiles>Create New
Input Profile name and Description if need
Check VMware 5.1 Cluster
Next
Input IDRAC Cred
Input ESXi Host Cred
Just Save and continue without test

If tested, it will fail to connect as below due to no CSIOR and OMSA Agent installed on the ESXi Hosts
Leave as default, and Click Save and Continue
Finish
Click Fix vSphere Hosts for Compliance on the Overview screen
Next
Uncheck to manually put in the maintenance mode and reboot Hosts
Finish to fix hosts
Monitor the tasks are running
Manually put each ESXi Host to Maintenance mode and reboot manually to complete the installation at a time.
Click Connection Profiles again and Test Connection Profile. And Click Test Selected
It will pass the connections as below
Inventory Scan will run automatically and will found 2 Hosts inventoried successfully as below task pane

Dell Firmware Updates from an ESXi Host

Enter ESXi2 to the Maintenance Mode.
Drag to Move the ESXi2 from VMware 5.1 Cluster to Maintenance Cluster
Go to Home>Inventory>Hosts and Clusters> select esxi1 and click OpenManage Integration Tab
Click Run Firmware update Wizard under Host Actions
Uncheck exit maintenance mode after firmware update completes option and click update
OK to continue
It will keep updating status on Recent Tasks
Reboot ESXi2 to continue firmware updates
But, I got an error as below
Then, the events log shows the following info.
To fix this issue, Go to Configuration Tab on the ESXi2>Networking>Click Properties of Standard vSwitch1
Select iSCSI_LUN_Redundancy Port and Edit
NIC Teaming Tab> move up vmnic1 from unused Adapters to Standby Adaptors to apply change
Yes to Continue
Repeat the same on iSCSI_LUN for vmnic5 to move up to Standby Adaptors
Do the same configurations change on ESXi1 as well
Then, try to run Firmware Update Wizard on Step4 above on ESXi2 again
This time it runs correctly as below and show the status is “in progress”
Then, it finally completed the Firmware update task
Run Firmware Update wizard again
Click Update from repository
Next
Click Check All Box to select all available upgrade
Select Apply Update(s) on next reboot option
Wait until all the pending patches were pushed to iDRAC
Reboot the host manually (Make sure the host is in maintenance mode and maintenance cluster to pause any alert generating)
After rebooting, repeat the above update steps till no further updates available.
After all done, move ESXi2 back to VMware 5.1 Cluster and exit out from the maintenance mode.
Do the same update task for ESXi1 as well