A single-switch topology is the simplest form of a tree-based network architecture. Also referred to as a star topology, 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.

A CN5000 Switch provides 48 native 400 Gbps ports for SuperNIC links (the connections between the Switch and each SuperNIC). Up to 32 of these ports can each be subdivided into two 200 Gbps ports, enabling cost-effective connection of lower-bandwidth SuperNICs. In either configuration, every host communicates through the central Switch, providing a straightforward, low-latency network design.

Scaling Beyond a Single Switch

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, no additional hosts can be connected without expanding the network. A common approach to scaling beyond a single switch is to connect multiple Switches together. The connections between Switches are known as Inter-Switch Links (ISLs). By adding Switches and ISLs, the fabric can support far more hosts than a single Switch alone.

The ISL Bandwidth Trade-Off

While adding Switches and ISLs increases network size, it introduces a new consideration: 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 trade-off 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 of Switches, a Fat Tree helps keep host-to-host communication balanced and allows network performance to scale as the fabric grows.