Decide whether Windows Network Load Balancing fits the application

Source facts

Windows NLB combines multiple application servers into one virtual cluster and distributes incoming requests among those servers. Microsoft identifies stateless applications, including IIS web servers, as a practical use case. Its guidance directs SDN deployments, non-Windows workloads, outbound NAT requirements, and certain non-TCP load-balancing requirements toward Software Load Balancer instead. Microsoft Learn.

Applicability

Record the application protocol, server platform, session behavior, and networking design before selecting NLB. Ask the application owner to describe any state that must survive a host becoming unavailable. Do not substitute a network feature overview for that application-specific assessment.

DSE recommendation

Prepare a short selection record comparing the documented NLB use case with the actual workload. Name the application instances and decide how their readiness will be evaluated. Define a maintenance exercise that removes one host while representative users continue working. Set an acceptance threshold for the application transaction, with a clear owner for investigation if the result differs.

Verification

Measure completed transactions and errors before, during, and after the approved host-removal exercise. Verify that the remaining hosts receive requests and that the returning host behaves as intended. Include a state-dependent transaction when the application has one. Retain the selected design and rejected alternatives.

Official references

Microsoft Learn: Network Load Balancing. Source reviewed September 8, 2026.