Software Defined Network (SDN) is technology to allow network devices to be managed through software application, thus making configuration process automated and faster.

Network devices have its own management plane, data plane and control plane. Traditional SDN decouples Control plane from all different devices and have all these control plane go live inside  SDN controller so the controller now take care of control plane  and run the routing protocols and do all the control plane related stuff and administer or push instructions down the devices.




This type of SDN is known as stateful approach where SDN controller acts as a control plane for each network device it manages. The SDN controller is responsible for translating policies into commands and pushed to the devices.

SDN controller communicates with the below devices through southbound interfaces .One of the popular SDN controller is called Open Daylight.

Open Daylight is an open source SDN platform, which can use the OpenFlow protocol protocol as Southbound Application programming interface(API) to communicate with network devices that support Openflow  protocol.

We have just talked about the south of controller, north of controller is the applications which communicates to controller through NorthBound Interfaces. Applications can use REST API to communication through Northbound Interface to controller.

REST (REpresentational State Transfer) APIs allows to communicate with SDN controller using http or https .Postman is such one of the application which can be used to communicate the SDN Controller through Northbound interface.

CISCO  takes a bit different approach of  their controller APIC (Application Policy Infrastructure Controller ) and APIC-EM(Enterprise Module) .

APIC and APIC-EM have control plane back to the devices means that control plane is not decoupled from the network devices as in traditional SDN.

Cisco Controller is Stateless approach where each network device has its own control Plane. SDN Controller send policies to the network devices, which are individually responsible for translating policies into commands.






This is APIC which is seen in Data center whereas APIC –EM is generally seen in Campus, LAN or remote offices.

The best part of the APIC-EM is that it can communicate with our traditional devices which do not speak open flow , means that there is no requirement to run Open Flow through southbound interface to communicate with network devices which does not speak SDN languages.



APIC –EM communicate to network devices through southbound interface using TELNET,SSH or SNMP. Whereas Northbound Interface still communicates with APIC-EM using  REST  APIs so in Nutshell Application can send the instruction  to APIC-EM  through Northbound interface using REST APIs ,further APIC-EM push  instructions  to get the required information through Southbound Interface using SSH, TELNET or SNMP which is generally OpenFlow in case of APIC .


Characteristics of APIC

  • For use in Data Centers
  • Typical Applications found on APIC:
    • Policy Manager : Contains policy and rules that can be applied to end point groups
    • Topology Manager :Maintains Information about the topology
    • Observer :Does Monitoring of ACI Components.
    • Boot Director :Used for firmware update and booting of spine or leaf.
    • Appliance Director :Responsible for set and control APIC cluster
    • VM Manager :This acts as intermediator between hypervisor and platform such as openstack.
    • Event Manager :Stores events and faults.
    • Appliance Element :Manages individual controller




APIC-EM is generally used in 2- Tier infrastructure where core and distribution switches are collapsed together.

Characteristics of APIC-EM

  • For use in campus ,LAN or WAN
    • Network Topology Visualization: Dynamically Learn Topology and give maps.
    • CISCO IWAN :Help to set up IWAN
    • Path Trace Application: It get path trace from any Point A to any point B.

APIC-EM Dashboard


Hope this post helped to get basic insight of Traditional SDN and CISCO approach  based APIC and APIC-EM and most importantly the difference between APIC and APIC-EM

Smiles 🙂

Categories: SDN Tags: , , , ,
  1. 13 Nov 2017 at 6:35 am

    Does APIC support spine and leaf architecture too?


    • 13 Nov 2017 at 2:21 pm

      ACI comprises of APIC, one or more leaf switches and one or more Spine switches…


  2. Sona
    15 Feb 2018 at 5:47 pm

    This comparison is awesome. Great job.


  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: