ACI can be configured in a few different ways, including the following:
- L2 Fabric: The L2 Fabric configuration or legacy mode has no routing or L3 concepts. Tenants are represented as a set of EPGs.
- L3 Fabric: The L3 Fabric configuration adds the L3 features available in ACI and the concept of tenants.
- Stretched Fabric: The Stretched Fabric design allows multiple fabrics (up to three) to be managed as a single fabric, even if the fabrics are in different locations.
- Multipod: This is a more fault-tolerant fabric utilizing multiple pods or fabric sets. Depending on the location of the switches and servers, multiple pods could be located on the same and/or different floors.
One of the main requirements of ACI is that it requires a minimum of three APIC controllers; this allows a quorum to be reached between controllers, so two controllers must have a configuration change before it can be applied. In a large deployment, up to five controllers are supported.