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Cisco ACI: Control Plane components

February 04, 2023 , ,

Cisco ACI: Control Plane components

The control plane of Cisco ACI (Application Centric Infrastructure) consists of several components that work together to manage and orchestrate the Cisco ACI fabric. The components are VXLAN, COOP, ISIS, DHCP, LLDP, OPFLEX

The Architecture Cisco ACI follows is Spine/leaf architecture. Spine-Leaf topologies are based at the near community structure. The time period originates from Charles Clos at Bell Laboratories, who posted a paper in 1953 describing a mathematical theory of a multi pathing, non-blockading, more than one-level community topology wherein to replace smartphone calls.

Spine-leaf is typically deployed as two layers: spines (like an aggregation layer), and leaves (like an get right of entry to layer). spine-leaf topologies provide excessive-bandwidth, low-latency, non-blocking server-to-server connectivity.

VXLAN in Cisco ACI
For L2 switching and L3 routing across the Cisco ACI fabric, VXLAN is also a component of the fabric. In MPBGP-EVPN, VXLAN is employed inside Cisco ACI.

A VTEP address will be allocated to each leaf/spine switch in the fabric from the pool of VTEP addresses set during APIC startup. This VTEP address will be utilized to route data plane traffic over the Cisco ACI Fabric using VXLAN.

Cisco ACI VXLAN
Fig 1.1- VXLAN in Cisco ACI

COOP (Council of Oracle Protocol) in Cisco ACI
Cisco ACI uses COOP (Council of Oracle Protocol) for the LEAF. The network endpoints that are directly or indirectly linked to the fabric's leaf switches are identified by their addresses.

Spine switches will use the COOP protocol to broadcast and learn the information from these EPs. COOP utilizes an additional VRF called a "overlay." To advertise the endpoint information throughout the Cisco ACI fabric, Cisco ACI automatically creates this vrf.

ISIS Protocol in Cisco ACI
To provide the architecture and adjacency between the leaf and spine switches throughout the network, the Cisco ACI fabric uses the ISIS protocol. ISIS assists in creating the adjacency database of the linked devices on the Cisco ACI network once the first discovery is complete. ISIS is only for managing infrastructure.

DHCP Service
Every leaf and spine has DHCP service activated by default. For VXLAN communication across the Cisco ACI fabric, this is enabled in order to retrieve the VTEP IP address from the VTEP pool specified on the APIC controller.

LLDP
On the leaf and spine switches, LLDP is by default turned on. Once the network's physical connectivity has been established, switches will use LLDP to find one another and register with the APIC controller.

OPFLEX protocol
Between the controllers and the leaf/spine, OPFLEX protocol is utilized. The leaf/spine switches get the Cisco ACI fabric configuration that was completed on the controller in the form of a GUI.

There will be an opflex agent operating within each leaf/spine switch. This agent is in charge of delivering the configuration across the network and turning the GUI/Scripting information into pertinent CLI that switches can understand.