An ACI switch is a networking device that forms part of a Cisco Application Centric Infrastructure (ACI) fabric, providing the physical connectivity layer for this policy-driven data center architecture.
In the context of Cisco ACI, the term "ACI switch" typically refers to either a leaf switch or a spine switch, which are the two main types of switches comprising the ACI fabric. Unlike traditional networks configured switch-by-switch, ACI switches are managed and controlled centrally by the Application Policy Infrastructure Controller (APIC).
Components of an ACI Fabric
According to the provided information, ACI consists of three key components:
- Application Policy Infrastructure Controller (APIC): A centralized controller that manages all aspects of the ACI fabric.
- Leaf Switches: These are ToR switches that provide connectivity between servers and external networks.
- Spine Switches: These switches interconnect the leaf switches in a spine-and-leaf topology.
Leaf Switches
Leaf switches are positioned at the edge of the ACI fabric. They connect to:
- Servers and end-points (like virtual machines, bare-metal servers, or appliances)
- External networks (via border leaf switches)
- All spine switches
As stated in the reference, leaf switches act as Top-of-Rack (ToR) switches, serving as the initial point of connection for devices within the data center and also providing uplink connectivity out of the fabric.
Spine Switches
Spine switches form the backbone of the ACI fabric. Every leaf switch connects to every spine switch in a full mesh topology. Spine switches do not connect to servers or external networks directly. Their primary role is to provide high-speed, non-blocking connectivity between leaf switches. This ensures that any leaf switch can communicate with any other leaf switch with minimal latency.
How ACI Switches Work Together
The spine-and-leaf architecture utilizing ACI switches offers several advantages:
- Predictable Latency: Traffic only needs to traverse a maximum of one spine switch to get from any leaf switch to any other leaf switch.
- Scalability: Adding capacity typically involves adding more leaf switches (for more server ports) or more spine switches (for more fabric bandwidth), or both.
- Centralized Management: The APIC manages the configuration and policy enforcement across all leaf and spine switches in the fabric.
In essence, "ACI switches" are the specialized hardware (leaf and spine switches) that build the physical network foundation for the intelligent, policy-based ACI data center solution.
