As network grow, Software-defined networking (SDN) becomes more popular and meanwhile Cisco ACI changes the way we’ve traditionally thought about networking. Previously, in Traditional networking administrators use commands and to manage different devices locally. Cisco Application Centric Infrastructure (ACI) is a holistic architecture in the data center providing centralized automation and policy-driven application profiles. This solution delivers software flexibility with the scalability of hardware performance. To fully understand the Cisco ACI, we should first get familiar with Spine-and-Leaf architecture.