Which Server OS is required for doing Windows NLB clustering ?

p1xels

Hi all,
I have been trying to practice NLB clustering by using Virtual Machines/Hosts.
For this purpose I used three(3) VM Servers with one acting as the DC(domain controller) and running the Server 2008 as OS & 2 web-servers each running the Windows 2003 r2 as OS. But I found that I cannot mix-n-match the different Server OS as then I cannot install the Web Server Role in the 2 client machines.
My teacher told me that I need to install the same Server OS in all the machines i.e. Windows Server 2008 (r2) installed .
My question is why do we need the same OS installed in all the machines and also why can't we use Server 2003 as OS? Is it mandatory to use only higher version of Windows Server OS like 2008/2008R2 or 2012/2012 R2 while doing NLB Clustering?

Thanks in advance
With Best Regards

JeanM

Normally you run the same OS when you create a cluster, but as an example here are step by step for 2003 and 2008, but not mixed.

https://technet.microsoft.com/en-us/library/cc725691.aspx

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Install and Configure WLBS (NLB) on Windows Server 2008 | JPPinto.com - Tech Blog

https://social.technet.microsoft.com/Forums/windowsserver/en-US/de8f99c9-fc3f-40fd-90c3-d79d508a8722/server-2008-into-a-nlb-cluster-of-server-2003-error-could-not-read-configuration-of-interface?forum=windowsserver2008r2highavailability