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I set up a NLB cluster given two servers (WS 2008 R2). Each server has one NIC card which I set up for a static ip address. I assigned the cluster an internet name (MyCluster), and assigned it a static ip address. The third box is acting as a client sending TCP data (over WCF) to the cluster's IP I configured (static IP). I am observing the NLB cluster from the NLB manager at one of the nodes - both nodes are green, say started. However, I am only able to see traffic coming in to one of the NLB servers. When I suspend it, I see traffic going to the other NLB server, and so on. I was expecting traffic to be split equally between them. I can't figure out what I missed, any tips please?


Port rules screenshot requested by joeqwerty enter image description here

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up vote 5 down vote accepted

If you want a single session to balance across the two NLB nodes, you will need to change the Client Affinity to None. That will allow each request to be answered by the first available node. Be careful though, if you are using sessions this can cause issues where only one node is aware of the session.

In my experience, I haven't observed NLB to work in Round Robin fashion. To force a single load balancing with a low # of clients rapid refreshing took about 30 seconds before load balancing started.

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Setting client affinity to "None" did it! ~ thanks. – sOltan Apr 22 '14 at 21:10
Also, my application services running on the cluster nodes are restful/stateless so I'm fine with the client traffic being handled by any one of them. – sOltan Apr 22 '14 at 21:11

That's not how NLB works. It does not load balance a single traffic stream across servers.

NLB load balances independent TCP or UDP sessions across the servers. So if you have two independent sessions then NLB should direct the first session to one server and the second session to the other server.

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Thanks. I just added a second client (I think that's what you mean by session), and now, traffic from both clients is still going to only one of the NLB servers. If I suspend that server, I see traffic going to the other NLB server. – sOltan Apr 22 '14 at 20:03
Can you post a screenshot of your port rule? – joeqwerty Apr 22 '14 at 20:25
joeqwerty, just did. – sOltan Apr 22 '14 at 20:36

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