Description of support boundaries for using Windows Network Load Balancer with Hyper-V Network Virtualization networks

Applies to: Windows Server 2012 R2 Datacenter


The Network Load Balancing (NLB) feature distributes traffic across several servers by using the TCP/IP networking protocol. By combining two or more computers that are running applications into a single virtual cluster, NLB provides reliability and performance for web servers and other mission-critical servers.

Hyper-V Network Virtualization (HNV) provides virtual networks to virtual machines similar to how server virtualization (hypervisor) provides virtual machines to the operating system. Network virtualization decouples virtual networks from the physical network infrastructure and removes the constraints of VLAN and hierarchical IP address assignment from virtual machine provisioning. This flexibility makes it easy for customers to move to Infrastructure as a Service (IaaS) clouds, and is efficient for hosts and datacenter administrators to manage their infrastructure while maintaining the necessary multi-tenant isolation, security requirements, and supporting overlapping virtual machine IP addresses.

More Information

The Windows Network Load Balancer is not supported for HNV networks. The Windows Network Load Balancer  implementation uses broadcast and multicast, and it requires each instance of Windows Network Load Balancer to share the same defined MAC address across its cluster. This use of broadcast and a shared MAC by Windows Network Load Balancer conflicts with the design of HNV because it requires L3 semantics in the Customer Address space and a single MAC address owner. 
HNV does support failover clustering for high-availability.