In my examples today I am going to use the tools directly built into ESXi and vSphere to get this done. I'm going to use PowerCLI 5.5 (latest version as of this writing) to get this done.
PowerCLI is one of the many tools that are bundled for free with the vSphere environment. I highly recommend you have it installed on your management server or workstation and if you're running vCenter on Windows it's even better to place it there. You can download PowerCLI from the VMware website.
The process of backing up and restoring the configuration is pretty simple so here we go.
Before running any of these commands you should run this command in PowerShell on Windows to make sure PowerCLI has the ability to execute the commands needed for this process to work.
Open PowerCLI and use the Connect-VIServer IPAddress command to connect to the server.
Next run the command below to backup your host's configuration. Make sure you create the backup location folder before you run the command.
Get-VMHostFirmware -VMHost ESXi_host_IP_Address -BackupConfiguration -DestinationPath “Output_Directory”
When the process completes you'll have files that look like this:
That's all there is to backing up the configuration of your ESXi host. Now for the really cool part.
If you're upgrading hosts to new hardware there a couple of things I've done and the restore has went off without a hitch. Make sure you have the VMware install on the new host at the exact same version as the host you backed up. If not this isn't a supported process but you can use the "-force" command at the end of the restore to make it do it anyway. The next thing is to ensure you have the network cables in the exact same port numbers as the old host. In other words port 0 on the old host should get the cable for port 0 on the new.
If you're unsure which cables correspond to which port, once you've migrated all VMs off of the old host you can look at the network configuration in the vSphere client and pull the cables one at a time. From there just label each one so you know where to put it in the new server.
Once you've got the new box cabled up, on the same build of VMware as the old server, and powered on here's all you need to do.
First put the host into maintenance mode. This is required or the next step will not work. You can use the hostname, IP address, or FQDN if you want.
Set-VMHost -VMHost esx1 -State “Maintenance”
Next enter the restore command.
-Restore -Force -SourcePath
Once you do this the host will immediately restart. During the restart it will import the backed up configuration prior to completing the loading process.
After the host has fully restarted you will be able to see that all of your prior settings have been restored including those many times complicated network, VLAN, and MTU settings.
On the hosts I have performed this on if they have local storage I have had to configure the large datastore again but given how much time this saves that's a minor thing to get the new server online much, much quicker.
Good luck with your upgrades!