Best practice is hardware loadbalancing appliance. The windows network load balancing in not recomendet for exchange 2010 cas anymore.
HLB ( hardware load balance ) solution, This is what is being recommended.
SLB ( Software load balance) solution, This is also recommended.
Windows NLB ( network load balancing) This is no longer recommended
If you have not see Rose Smith video presentation do not miss it , How Outlook connects to Exchange 2010 Client Access Server
The main reason why HLB & SLB are recommended , these solutions provides “ Application awareness” and also managing CAS servers behind these type of deployment is very easy and efficient.
MAPI Request comes to HLB , HLB has CAS servers published within , Administrator easily can stop MAPI request going specific CAS server etc. These deployments are also far more stable and easy to configure IMO. I think we will see more official statement soon and expecting to see ending support recommendations to HLB with CAS in the near future.
