Configure Windows Network Load Balance (NLB)
Posted by Brajesh Panda on December 31, 2009
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!
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.
HLB: No worries like this in
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.
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
WNLB: No Web Acceleration
HLB: Web Acceleration by Caching
WNLB: No SSL or other encryption offloading
HLB: SSL Offloading & other firewall/security level configuration can possible