Microsoft Network Load Balancing

I believe there is a feature that can be enabled in the 3.7.7 8600 code that will assist in MS Load Balancing operations. I do not have the release notes in front of me, so I can not comment on the specifics.

We ran MS LB on our 8600s and BPS2ks for a number of applications. We had to create VLANs for each set of load balanced front-end nodes to control the level of broadcasts. It really was not so bad, except that it chewed up a lot of IP space. Once we figure out how the system 'tricked' the switches into flooding inbound requests, it really was not difficult to troubleshoot.

Since then, we have converted everything over to Alteon based solutions, which is far more flexible than the MS solution.

-mike

Hi. The short version is: Do NOT use MS load balancing ! It is an abomination, that violates all normal rules for layer 2 networking. The only way i have managed to get it to work, is by using an ethernet hub. So what's the point? And believe me, it's not for lack of trying!

If you realy need load balancing, get an Alteon switch and use that.

Regards MRN

Perhaps you can point me in the right direction to get this MS NLB to work. I did create a VLAN, say, vlan 1234 with port 1/3 & 1/4 port as its members on an access switch instead on the Passport directly.

Next, how do you trick the switch to be able to handle the MS NLB?

Thanks

Copy and paste from the Managing Platform Operations PDF (Part No.

Microsoft* Network Load Balancing Support

Passport 8000 Series switch software allows you to choose whether ARP entries for multicast MAC addresses are associated with the VLAN or the port on which it was learned.

This enhancement is useful if multiple endstations/servers are sharing a multicast MAC address as is the case with certain Microsoft network load balancing applications, wherein the traffic is flooded to the VLAN to ensure that every endstation using this virtual multicast MAC address is receiving a copy of the stream.

This feature is disabled by default.

To enable or disable NLBS support, enter the CLI command: config ip arp multicast-mac-flooding

Note: This option is not dynamic. That is, if the setting of this feature is changed, it will not dynamically reprogram all previously learned ARP entries from multicast MAC addresses.

The MS LB application will 'trick' the switches on its own. There is no additional configuration of the network gear required. Just isolate the front end nodes into their own VLAN. Observe the L2/L3 forwarding tables on the switches and compare them to the L2/L3 addresses on the front end nodes. You will see how the application will trick the switches into continuously flooding traffic to all the nodes on the VLAN.

In my opinion, it is a poor solution to load balancing. Keep in mind, my testing was with Windows 2000 Server, not 2003. MS might have changed their app a little bit. An Alteon type solution is going to be far more efficient.

-mike