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I have an NLB configured for two web servers. The NLB is a software NLB configured on Windows Server 2008 R2. The web servers are IIS servers. For a request of 5000 users, all my requests are going to one web server. So when does NLB send requests to other server. Also how do I configure NLB for sticky sessions ?

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up vote 2 down vote accepted

NLB will distribute the load according to the chosen filtering mode & affinity settings for your NLB cluster. If you've set "Single" filtering mode, all traffic will go to a single server. If you've selected "Multiple host", the affinity decides which host will receive the traffic of recurring users. If you've chosen Single/Class C affinity, all users from the same IP / IP class C range will hit the same server (beware proxies & internal network topologies in this case).

Furthermore, even in multiple host mode, you can choose a distribution factor under the port rules so one server may be at 100% while the other is at 0%.

I've got a short video on my blog on how to setup a simple NLB cluster that shows the filtering mode & affinity settings:

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Where do the requests come from?

NLB usually balances requests based on the client IP address (although this can be configured), so, if f.e. you're stress-testing it from a single machine, or if you have a reverse proxy which doesn't pass on the original caller IP, your requests will always be handled by a single server.

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Comments from Mark S. Rasmussen helped in configuring NLB properly. Now how showuld we configure sticky session on NLB?

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