This is the first volume of the Blockchain: The Hidden Gem of Data Networking series of eBooks. In this series, we will thoroughly define blockchain and see it in action; well see how blockchain could be leveraged to enhance the technologies that exist in the Data Networking: i.e. LAN and WAN technologies. In this first volume with subtitle BLAN (short for Blockchain-VXLAN); well see how we could leverage blockchain to create an architecture that connects geographically dispersed layer-2 islands over any available infrastructure (even the global public Internet). Connecting layer-2 islands is not a new approach, weve seen many successful solutions that fall under the Overlay Networking Technologies umbrella like: VXLAN, NVGREIn this volume, well see BLAN that is the result of the integration of blockchain with VXLAN. VXLAN was originally drafted as an overlay networking technology that can work without a control-plane and its scope is usually within a single administrative domain i.e. Data Center or Cloud. BLAN can greatly enhance the operation of the VXLAN technology by adding a control-plane component to it, and it can also extend VXLAN working domain beyond the boundary of a local Data Center (or even a public cloud). BLAN operation across the public Internet makes it more appealing as a viable WAN option for many customers (SME, large enterprises, service providers, Telcos) in front of conventional WAN options (like: Dedicated links, MPLS or VPN across the Internet) or modern options (like: SD-WAN).