As organizations migrate to all-digital solutions in areas like cloud, mobility, and Internet of Things (IoT), the strength of the network hosting these technologies will be more critical than ever. The traditional network engineering model of configuring one device at a time simply doesn’t scale to the growing needs of today’s network. Cisco's intent-based networks and software-defined networking solutions will enable your organization to meet the demands of network programmability and automation. The result will be greater network agility to support new applications while complying with increasing security needs.
What is software-defined networking?
Software-defined networking (SDN) is a new approach to the network infrastructure and protocols that make networks more agile, add simplicity to the networking protocols and allow bandwidth to scale exceptionally high.
The defining characteristics of SDN are two types of protocols—underlay and overlay—that work together as a powerful team. Simply put, an underlay is a protocol that runs lower on the OSI model, typically right above Ethernet. An overlay is a protocol that runs higher in the OSI model, analogous to an application running on UDP.
The most popular overlay is Virtual Extensible Local Area Network (VXLAN). While a VXLAN extends a layer 2 network like a VLAN always has, VXLAN improves on a VLAN in several ways. First, the total number of VLANs is a 12 bit field or 4,096. The VXLAN standard allows for 24 bits, or 16,777,216 total VNIs. A VNI is called the VXLAN network identifier.
While VLANs stop at a router, VXLAN is a tunneling protocol that can go over routers, allowing VXLAN to extend a layer 2 subnet within or to another data center. VXLANs have no distance limitations and VXLANs never block a port like spanning tree does.
Another example of an overlay is Network Virtualization using Generic Routing Encapsulation (NVGRE). Like VXLAN, NVGRE is also a tunneling protocol.