Tuesday, October 13, 2009

Windows Load Balancing Server 2003 and Server 2008

1) Server 2003 - suggests two network adapaters one to listen and one to speak.

2) Server 2008 - says you really only need one network adapater.  If you need two, you'll need to enable IP Forwarding (see below).

from http://www.numtopia.com/terry/blog/archives/2008/10/windows_2008_nlb_with_2_nics.cfm

I worked with our networking team, and they figured out (from this post: http://social.technet.microsoft.com/Forums/en-US/winserverClustering/thread/0afdb0fc-2adf-4864-b164-87e24451f875/ ) that if you added a gateway to the cluster NIC, it would work. This is counter to the way NLB has worked before, and generally not best practice. So we opened a support case with Microsoft. After a few tries, I finally got an engineer that was an expert on NLB in 2008, he had the exact cause and solution for this problem: by default IP Forwarding is not enable in Windows 2008. This is the feature of Windows networking that, in the context of NLB, allows responses to requests sent to one NIC to be routed out the other. It's fixed by using one specific command line option.

(Make sure you are using a command prompt with administrative privlidges)

netsh interface ipv4 set int "[name of the NIC]" forwarding=enabled

3) Another option would be ISA or ARR appears to be able to load balance traffic for you.  when making a rule (with the newest service pack) it asks for a list of servers in a farm (as opposed to the single virtual IP).