Tip of the Day: Windows Server Hyper-V SR-IOV and SDN

Today's tip...

Question of the Day:


My customer has a variety of applications in its organization and some have low latency networking requirements. The customer is interested in setting up a private cloud using Windows Server 2016 and System Center 2016. The main purpose of the cloud is to offer IaaS/VMs to some tenants including apps with low latency networking requirements. My customer is looking at SR-IOV and wondering how it interacts with Windows Server 2016 SDN. If the customer gets NICs that support SRIOV, can the VMs still leverage these features if they’re using Software Defined Networks using NVGRE/VXLAN?


Good question. If your customer plans to leverage Hyper-V’s SDN features, keep in mind that Single Root IO Virtualization (SR-IOV) and SDN are mutually exclusive.

  • With SR-IOV, network traffic bypasses the virtual switch.
  • SDN requires the virtual switch to perform network virtualization.

It’s explained in the following document: https://gallery.technet.microsoft.com/Network-Offload-and-85749147

This is the key section:  Traffic that uses SR-IOV bypasses the Hyper-V switch. That means that any policies (ACLs, etc.) or bandwidth management won’t be applied.  SR-IOV traffic also can’t be passed through any network virtualization capability so NV-GRE or VxLAN encapsulation can’t be applied. Since the host policies, bandwidth management, and virtualization technologies can’t be used, this is a tool only for very well trusted workloads in very specific situations.