Cisco 3K is a series of modular switches from Cisco Systems. It is designed to provide high performance, scalability, and flexibility for enterprise networks. The 3K series includes the Catalyst 3K-X, 3K-E, and 3K-L switches, which offer a range of features such as advanced security, virtualization, and energy efficiency. The 3K series is ideal for large-scale deployments, as it can be easily scaled up or down to meet changing network needs. It also offers a wide range of features such as Layer 2/3 switching, VLANs, QoS, and more. With its robust design and features, the Cisco 3K series is an excellent choice for enterprise networks.