Network Load Balancing, intermittent port problem on Windows Server 2008

nlbwindows-server-2008

Trying to troubleshoot an intermittent problem on a Windows Server 2008 NLB. I think it might be related to an NLB issue. We are using Windows Network Load Balancing to balance load for our multiserver SharePoint front ends.

Say… Web Front End 1 IP is 192.168.1.100 and Web Front End 2 IP is 192.168.1.101, the NLB is setup to load balance both WFE servers on any incoming traffic to the IP 192.168.1.200.

Sometimes we got an intermittent issue where when we try to access the SharePoint site using 192.168.1.200:8080 (say the site is set up to run on port 8080) from a remote client, it will display page not found.

Pinging the 192.168.1.200 will give responses, but when trying to telnet to 192.168.1.200:8080 it just won't connect.

However, browsing the SharePoint site directly on individual WFE (192.168.1.100 and 192.168.1.101) show no problem whatsoever.

My guess also (we didn't get a chance to try it yet, but I think it should work), if I try connecting remotely to individual server, it will respond just fine.

But any attempt on trying to connect using the virtual IP (192.168.1.200) will fail miserably.

Funny thing is, after a while it will return back to normal.

Anyone had similar experience with this type of problem while implementing NLB before?

We are doing this in a virtual environment.

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