Windows 2000 NLB issue

[iangh2]

We have a cluster of 2 Windows 2000 servers running NLB which are flooding packets across our LAN (Cisco 3550 switches configured as Layer2). The NLB servers have 1 NIC each and are configured as Unicast.

According to Microsoft & Cisco this can be overcome by connecting both servers to a hub, connecting the hub to the switch and configuring the servers so that the SourceMAC address is hidden. Theoretically allowing the NLB cluster to only be seen from one Layer2 switchport which will stop the port flooding. I'm going off this:

http://support.microsoft.com/kb/193602/en-us

The problem that we have is that when we configure this up, only one server from the cluster responds to any requests.

Anyone come across this or have any suggestions?

Thanks

 

[iangh2]

Hi - anyone able to help on this one?

Thanks

 

[ADB100]

This is a common problem with badly designed implementations of NLB. Unfortunately it is tricky to resolve if you want to keep the big Layer-2 network. Windows 2003 introduced IGMP support when using Multicast & NLB but that requires mutlicast routing & IGMP capable routers/switches.

The best way around this is to put the servers on their own VLAN and make sure this VLAN's diameter is small and only goes to the 1 or 2 switches where you have the servers connected (remove the VLAN from ALL other trunks).

I have seen this so many times recently and it has been due to the lack of knowledge of the people who put the solution together. The best so far has been a backup scenario where a gigabit connected server was writing to the Virtual Cluster Address that isn't resolvable from a Layer-2 perspective and the traffic had to be flooded throughout an entire flat network.....

HTH

Andy