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1. The NLB licensing option in Sitefinity provides the cache invalidation mechanism required for Sitefinity to work in load balancing environments, but it does not implement any load balancing features. It ensures that separate instances of Sitefinity when running on hosts in load balancing environment do not cache content that was already changed on other instance.
2. On the question do you need to buy anything else - from the Sitefinity side - answer is 'No'.
3. To use Sitefinity in NLB you have to deploy it in some sort of NLB environment. For example NLB Manager is not present in Windows 7, but in Windows Server line of products. I recommend to check with your system or network administrator do you have the software or hardware ingredients needed for network load balancing.
4. For the sake of other readers in the forum will post here the starting article of Sitefinity documentation about Network Load Balancing:
And let me know if you have further questions.
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