How SCCM differentiate one client from another? Is it by name, IP or mac address?

Differentiate what ? can you be more specific what are you trying to do ? It will not differentiate any but you must make sure there are no duplicate computers means obsolete computers etc. SCCM client must be active (must not name resolution issues )to communicate with SCCM server. http://eskonr.com/2014/03/sccm-configmgr-2012-delete-duplicate-obsolete-records-etc-using-collections/

Each client has it's own Resource ID.

• Proposed as answer by Jörgen NilssonMVP, Moderator 1 hour 46 minutes ago

Each client has it's own Resource ID.

• Proposed as answer by Jörgen NilssonMVP, Moderator Monday, August 24, 2015 6:02 AM

Each client has it's own Resource ID.

• Proposed as answer by Jörgen NilssonMVP, Moderator Monday, August 24, 2015 6:02 AM

ResourceID is also unique, but it's the SMS GUID.

I ask this question because I have windows server image used as a template. Also the sccm client is already installed in the template. During the process to deploy the template I run sysprep after add the device in sccm by his mac address. The problem is that I see 2 times the same device in sccm. Is it because the client was already installed in the template?

First, you should sysprep *before* you capture an image but before you do this you need to prepare the ConfigMgr client agent to live in the image: https://technet.microsoft.com/en-us/library/gg712298.aspx (under the How to Install Configuration Manager Clients Using Computer Imaging section).

Hardware IDs are generally used to differentiate different managed systems but there is intelligence built-in that will match up resources based on AD SIDs. The ultimate client side identifier is the certificate thumbprint (either PKI or self-signed).

Let say I have a VMWARE template with Windows OS and SCCM agent already installed. So the only thing I need to do to make sure SCCM will just see one device is a SYSPREP. Is that right?

in simple terms... using MAC address/GUID/SID

if there are any duplicates... you may see errors

So I can leave the sccm agent in my template. The most important part is SYSPREP.

No, see the section about 'imaging': https://technet.microsoft.com/en-us/library/gg712298.aspx

That depends about when you are talking about using sysprep. Ultimately, ConfigMgr itself shouldn't be affected; however, to be supported, the image you deploy must be syspreped. That should happen before you capture the image though, not after. Thus the image in the template you are using must be syspreped.

The section that Torsten is referring to is "How to Install Configuration Manager Clients by Using Computer Imaging".  Honestly your safest and best bet would be to rip it off of the image, Sysprep your template/image and then have a automatic task after to apply the Client (startup script/Software updates are best bets).  Or even a SCCM task sequence to apply the sysprepped image to the VM?

Suppose I leave the client in the template and do SYSPREP from a clone of the template. Is SCCM will detect the new device automatically or I have to import it in SCCM?

Follow the steps mentioned in the article I've posted. You might run into issues if you don't.

Once again, you don't sysprep *after* deploying the image, you sysprep *before* capturing the image. But this really has nothing to do with ConfigMgr however you won't be supported if you don't sysprep and *will* run into various issues.

All thanks to all for your help.