A single-switch topology is the simplest form of a tree-based network architecture. Although it is not usually referred to as a 1-tier tree, it serves as the foundation for larger hierarchical designs. In this configuration, all hosts connect directly to a central switch, creating a layout that can be visualized as a hub surrounded by endpoints.

For example, a CN5000 Switch supports up to 48 native 400 Gbps SuperNIC links (connections between the Switch and SuperNIC) or up to 80 subdivided 200 Gbps SuperNIC links. In either configuration, every host communicates through the central SuperNIC, providing a straightforward, low-latency network design.

The primary limitation of a single-switch topology is scale. The maximum size of the fabric is constrained by the number of available Switch ports. Once all ports are occupied, additional hosts cannot be connected without expanding the network. A common approach to scaling beyond a single switch is to connect multiple Switches together. Connections between Switch are known as Inter-Switch Links (ISLs). By adding switches and ISLs, the fabric can support a larger number of hosts than would be possible with a single Switch alone.

While this approach successfully increases network size, it introduces a new challenge: the bandwidth available between Switches is limited by the number and capacity of the ISLs. Hosts connected to different Switches must share this inter-switch bandwidth when communicating with one another. As the network grows, insufficient ISL capacity can create bottlenecks, resulting in congestion and reduced application performance. This limitation is one of the primary reasons hierarchical topologies such as Fat Trees are used in large-scale deployments. By increasing the bandwidth available between higher tiers ofSwitches, Fat Trees help ensure that communication between hosts remains balanced and that network performance scales as the fabric grows.