Configure Windows Network Load Balance (NLB)


People used to keep me asking about “how to configure NLB for web servers?”. I will be releasing my step by step guide for the same. But for time being you can refer to a very good article over here. (http://www.west-wind.com/presentations/loadbalancing/networkloadbalancingwindows2003.asp)

Here are some merits & demerits of Windows network load balancer & hardware load balancer!

Point 1:

WNLB:  broadcast the request to all the servers in the cluster and one of the servers says I receive it.

So Server must be connected to a network switch which allows Broadcast (at least in the same subnet) like Layer 2 Switches.

So if your switch is a layer 3 switch your cluster will never work. To make this work issue you need to create a Layer 2 VLAN in your Layer 3 switch.

http://social.technet.microsoft.com/Forums/en/exchangesvravailabilityandisasterrecovery/thread/6277b695-8f18-413d-9be0-deeba2d284ef

HLB: No worries like this in

 Point 2:

WNLB: is not application aware. Means even if application is already dead but server is live, it will still send packets to the server.

HLB: You can configure application verification (by teleneting to 80/443 port etc) to see if application is live or not. If application dead it will assume server is dead.

Point 3:

WNLB:  Network Card GUID issue. If you deploy virtual machine or ghost copies some time you may end up with same network card guid in registry & it create conflict in windows load balancing technique.

HLB:  No issues because virtual is bonded to network IP

Point 4:

WNLB: No Web Acceleration

HLB: Web Acceleration by Caching

Point 5:

WNLB: No SSL or other encryption offloading

HLB:  SSL Offloading  & other firewall/security level configuration can possible

Another Good Link: http://aliayman.blogspot.com/2010/01/network-load-balance-and-layer-3-switch.html

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