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NVGRE

What is it?

NVGRE is a software controlled network virtualization framework that supports multi-tenancy in networks using Generic Routing Encapsulation (GRE)

What problem does it solve?

NVGRE is Microsoft’s solution to allow seamless migration of workloads between public and private clouds. It offers the same benefits associated with other Virtualization Overlays, such as:

  1. Multi-tenant isolation
  2. Layer 2 Scalability
  3. Removing the limitation of 4094 logical networks in a Data Center

For more information on virtualization overlays in general click here.

NVGRE Packet

NVGRE as you can probably guess uses GRE as it’s encapsulation to extend the Layer 2 network. Other than that as you can see by the packet below, it’s pretty similar to VXLAN.

GRE - NVGRE (1)

Key Components

  • Virtual Subnet Identifier (VSID): The VSID is a 24 bit identifier associated with every layer 2 network. Used to uniquely identify the tenants subnet to various devices in the subnet.
  • NVGRE Endpoint (NVE): The NVE is A Gateway between the virtual and physical network. Primary function of this endpoint is to encapsulate Ethernet frames into the GRE tunnel and apply network isolation by imposing a VSID.

How it works

As you can guess the set up is pretty much the same as VXLAN, The only key difference being the use of GRE, otherwise you can pretty much exchange the terms. To that end if you have not looked at the VXLAN post, please click here to see an overview of how this technology works.

Who supports it?

  • Microsoft

More information

RFC 7637 NVGRE: Network Virtualization Using Generic Routing Encapsulation

About Stephen Ransome

Stephen Ransome is an IT consultant and network nerd with experience ranging from SMBs to Service Providers, he has a passion for learning new technologies and delivering solutions that count. He has some alphabet soup, including CCIE#41102 and is far more cynical than he should be.