# Network Virtualization ## What is Network Virtualization Network virtualization is the process of combining hardware and software network resources and network functionality into a single software-based entity called a virtual network. It allows multiple independent virtual networks to run on the same physical network infrastructure. Each virtual network is isolated from the others and behaves as if it has its own dedicated hardware. Network virtualization makes networks more flexible, efficient, and easier to manage. ## Types of Network Virtualization External network virtualization combines multiple networks or parts of networks into a virtual network. Internal network virtualization provides network-like functionality to software on a single server. This includes virtual switches and virtual network interfaces within a hypervisor. Network function virtualization moves traditional network functions like firewalls, load balancers, and routers from dedicated hardware appliances into software running on standard servers. ## Network Function Virtualization Network Function Virtualization or NFV replaces dedicated network hardware with software running on standard servers. Instead of a physical firewall appliance, an organization runs firewall software on a virtual machine. Instead of physical load balancer hardware, they run load balancer software. NFV allows network functions to be deployed quickly by spinning up virtual machines rather than ordering and installing hardware. Functions can be scaled up by adding more virtual machines or scaled down by removing them. NFV reduces capital expenditure by using standard server hardware instead of expensive specialized appliances. ## VXLAN VXLAN stands for Virtual Extensible LAN. It is an overlay network technology that encapsulates Layer 2 Ethernet frames inside Layer 3 UDP packets. This allows virtual machines to communicate over Layer 2 even when they are connected to different Layer 3 networks. VXLAN is widely used in data centers to support large numbers of virtual networks. It supports up to 16 million unique VXLAN segments, compared to the 4094 VLAN limit of 802.1Q, making it suitable for multi-tenant cloud environments. ## VMware NSX and Similar Platforms VMware NSX is a network virtualization platform that implements an entire network stack in software. It provides virtual switches, distributed routers, firewalls, load balancers, and VPN services entirely in software running on hypervisors. The physical network provides only basic IP connectivity. All other network functions are handled in software. This allows network configurations to be created, changed, and deleted in seconds through a management interface, independent of the physical network hardware.