Comparison of Leaf Interfaces vs Spine Interfaces in Cisco ACI

In Cisco ACI, under Fabric > Access Policies > Interfaces, administrators configure how switches connect to endpoints and each other. This section is divided into Leaf Interfaces and Spine Interfaces, each serving distinct roles in the ACI fabric. Understanding the differences between these interface types is crucial for proper policy application and network design.

Leaf Interfaces

Leaf Interfaces are used to connect endpoints such as servers, firewalls, routers, and external switches to the ACI fabric. They support various interface types including Ethernet, Port-Channels, and Virtual Port Channels (vPCs). Policies such as CDP, LLDP, Port Channel, and Storm Control are applied to these interfaces through Interface Policy Groups.

Spine Interfaces

Spine Interfaces are primarily used to connect leaf switches and occasionally external routers for advanced routing scenarios. These interfaces typically use high-speed Ethernet connections and are configured with spine-specific interface policies. Unlike leaf interfaces, spine interfaces do not connect directly to endpoints.

Summary Comparison Table

Feature	Leaf Interfaces	Spine Interfaces
Connects To	Endpoints (servers, routers, firewalls)	Leaf switches, external routers
Policy Types	Access Port, Port Channel, vPC Policy Groups	Spine Interface Policy Groups
Use Case	Endpoint connectivity	Fabric backbone and routing infrastructure
Interface Types	Ethernet, Port-Channel, vPC	High-speed Ethernet