What is a Virtual Network?
A virtual network is, as the name suggests, a network constructed virtually. However, there are multiple definitions and implementation methods for this concept.
One of the earliest forms of virtual networks emerged in the mid-1990s with the introduction of VLAN technology, which allowed physical L2 switches to be logically divided into multiple L2 segments. These virtual networks are commonly referred to as VLANs.
With the widespread adoption of server virtualization, networks virtually connected to virtual machines (VMs) operating on a hypervisor have also come to be called virtual networks. In virtualized environments, the physical server’s network interface is shared by multiple VMs. To enable this, each virtual machine is allocated a logical network interface (virtual port). These virtual ports connect to a virtual switch running on the hypervisor, forming a virtual network.
The introduction of technologies like VXLAN (Virtual eXtensible LAN) and NVGRE (Network Virtualization using Generic Routing Encapsulation) has further expanded the flexibility of virtual networks by allowing highly customizable virtual environments on top of existing physical networks or VLANs. Networks created with VXLAN or NVGRE can be dynamically generated and deleted via software, and such networks are referred to as overlay networks.