ABC of Cisco ACI Fundamentals

What is Cisco ACI?

Cisco ACI is the solution that emerged from Cisco, following its acquisition of Insieme, which is

a company they funded for more than two years.

ACI is seen by many as Cisco’s software-defined networking (SDN) offering for data center and

cloud networks.

How Cisco ACI Works?

Cisco ACI is a tightly coupled policy-driven solution that integrates software and hardware.

The hardware for Cisco ACI is based on the Cisco Nexus 9000 family of switches.

The software and integration points for ACI include a few components, including Additional

Data Center Pod, Data Center Policy Engine, and Non-Directly Attached Virtual and Physical Leaf

Switches. While there isn’t an explicit reliance on any specific virtual switch, at this point,

policies can only be pushed down to the virtual switches if Cisco’s Application Virtual Switch (AVS)

is used, though there has been talk about extending this to Open vSwitch in the near future.

To a large extent, the network for Cisco ACI is no different than what has been deployed over

the past several years in enterprise data centers. What is different, however, is the management

and policy framework, along with the protocols used in the underlying fabric.

In a leaf-spine ACI fabric, Cisco is provisioning a native Layer 3 IP fabric that supports

equal-cost multi-path (ECMP) routing between any two endpoints in the network, but uses

overlay protocols, such as virtual extensible local area network (VXLAN) under the covers

to allow any workload to exist anywhere in the network. Supporting overlay protocols is

what will give the fabric the ability to have machines, either physical or virtual, in

the same logical network (Layer 2 domain), even while running Layer 3 routing down to the

top of each rack. Cisco ACI supports VLAN, VXLAN, and network virtualization using generic

routing encapsulation (NV-GRE), which can be combined and bridged together to create a logical

network/domain as needed.