Refreshing my memory on cisco ACI

Almost been a year that i was trained on ACI, hence, would like to refresh my memory before its completely ¬†wiped off ūüôā

My first impression, i felt the product was quite interesting because simplification of networking configuration/application ¬†driven policy/Micro segmentation/Multi-tenancy/automation…

My view,  takes little time to understand for core networking folks but the person who is from Core Network + virtualization  cloud able to understand the concepts well and able to integrate ACI with different hypervisors with ease(VMvamre vSwitch/Hyper-v,Xen,Openstack(Neutron Component as well)

What is ACI??? 

Application Centric Infrastructure (ACI) in the data center is a holistic architecture with centralized automation and policy-driven application profiles. ACI delivers software flexibility with the scalability of hardware performance.

Key characteristics of ACI include:

  • Simplified automation by an application-driven policy model
  • Centralized visibility with real-time, application health monitoring
  • Scalable performance and multi-tenancy in hardware

Works on eVxlan, it extension of Vxlan

In simple, what is Vxlan:

VXLAN enables you to create a logical network for your virtual machines across different networks. You can create a layer 2 network on top of your layer 3 networks. This is why VXLAN is called an overlay technology. Normally if you want a virtual machine to ‚Äútalk‚ÄĚ to a virtual machine in a different subnet you need to use a layer 3 router to bridge the gap between networks.

  1. Each VXLAN(Virtual extension lan) is LAN extension over L3 and  segment has unique  24-bit Virtual Network Identifier(VNI) enables up to 16 Million  unique virtual LAN segments.
  2. VXLAN uses MAC over IP/UDP.
  3. VXLAN is first host based overlays means,VXLAN  encap and decap starts from physical server and virtual switch sitting on physical server.
  4. Enables VM mobility at layer 2 across layer 3 boundaries

For more information on Layer2 over Layer 3 protocols, please go through Massive data center design book which covers(TRILL,Fabric path, VXLAN,NVGRE)



ACI infrastructure essentially has 3 components:

  • Spine Switches (SPINE -> 9500 series, Baby Spine -> 9336PQ)
  • Leaf Switches (LEAF -> 9396 (2U) & 93128 (3U))
  • Application Policy Infrastructure Controller – APIC Cluster (min 3 devices in a cluster)
  • As of now 6 Spines and 18 leaves are supported in an ACI fabric. The ratio of Spine to Leaf is 1:3
  • Support upto 1000 tenants and 128K End point
  • North bound ports on the Spine are always 40 Gig while South bound ports on the Leaf for Access layer are 1/10 Gig
  • ACI also comes with a different line card which is other than the conventional Nexus line cards
  • Leaf and Spine switches communicate with each other through IS-IS protocol
  • Please refer below link for more information
  • NFE -> Switching (Broadcom T2), ALE -> Routing (Cisco)

Hardware information:


Partner Ecosystem(stale data): uses oplex protocol(Cisco ) for integration, as per my knowledge, ACI does not support openflow protocol.

L4-L7 Compatibility List:

Vendor Products Software First Certified APIC Release Link to the Device Package
Cisco ASA 5585 and ASAv ASA 5585 – 8.4 and later

ASAv – 9.2.1 and later

1.0(1x) ASA Device Packages
A10 Thunder Appliances – Hardware, Hybrid Virtual, Virtual 1.0 and later 1.0(1x) A10 Networks Device Package
AVI Networks 15.1 and later 1.0(2x) AVI Device Package
Citrix NetScaler MPX, SDX, VPX 10.1 and later 1.0(1x) Citrix Device Package
F5 BIG-IP LTM Physical and Virtual 11.4.1 and later 1.0(1x) F5 Device Packages
Radware Alteon VX and later 1.0(2x) Radware Device Package
As we all are aware of that ACI works on Declarative  model but what is the difference between imperative and Declarative model
ACI terminology(Depicted in different format for better understanding):
Teneant – Can be customer/BU/Environment(prod/Dev/Test)
Context/Private Network – Nothing but VRF in networking terminology
Bridge domain – SVI, a container for subnets
EPG(End point group) –¬†EPG`s are used to group end points (such as physical hosts or VMs together with similar policy requirements.
Contract – Policies between EPG`s,we can call it as ACL also.
¬† ¬† ¬† ¬† -Consumer –> Outgoing
¬† ¬† ¬† ¬†– Provided ¬†–> Incoming

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