Better late than never

I was working on an issue with Windows Server 2008 Network Load Balancing (NLB). Things weren't going so well when I used the same methods that I've used with Windows Server 2003. I first got it to work by assigning a second default gateway, which is not really a valid configuration. Since I didn't want to leave it that way, I went digging for some detailed information.

After piecing together information from various sources, it turns out that IP forwarding is not enabled by default on Windows Server 2008. The following command enabled IP forwarding on the network interface.

netsh interface ipv4 set interface "NLB NIC" forwarding=enabled

Some management always wants a good source before they will sign off on anything, and various blogs and forum posts don't always count. Technet blogs seem to have the credibility they are looking for. You'd think that paying $180/hour for a consultant would be credible enough when he said that this is what you need to do! Well, the good news is, some of the good folks at Microsoft have posted the setting on their technet blog.

http://blogs.technet.com/networking/archive/2008/11/20/balancing-act-dual-nic-configuration-with-windows-server-2008-nlb-clusters.aspx

Now I have something more than, "trust me, I know what I'm doing" when I run into this again. Also, for the folks who are stuck in the Windows NT 3.51 days, they show you how to make the change via the registry editor.

Key name: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
Value Name: IpEnableRouter
Data Type: REG_DWORD
Value: 1

I'm so happy the came out with the netsh command.