Refreshing my memory on cisco ACI (part – II)

I am trying to recollect some more points on ACI which is continues to my previous post.

ACI is a simple modular switch, below depicted diagram suppose to be in part -1  🙂

ACI - Modular switch

AVS -> Application Virtual Switching supported only on VMWARE (VEM)

  •         Essentially a modified N1K VEM with an Opflex agent (port-groups backed by VxLANs)
  •       APIC will also talk to AVS/VEM over OPFLEX and assign it IP address just like any other f    Fabric component

AVS flow

AVS switching modes:

  •            Local switching: Intra-EPGs traffic switched on the same host
  •           FEX mode: All traffic sent to Leaf for switching
  •           Full switching : : Full APIC policy enforcement on server


  • X9700 only supported ACI supported line card
  • NXOS line cards are different that ACI line cards
  • Leaf and Spine communicate over IS-IS (by default) and IBGP (configurable for route leaking)
  • Traffic is normalized into eVXLAN (ACI VXLAN) at the spine and communication happens based on source and destination EPG
  • If leaf does not know dest mac, traffic is sent to spine
  • If even spine does not know, then the frame is dropped by default, however we can configure it to flood such frames
  • Leaf identifies a new host as it comes up with any snooping technology and reports the Spine through a communication protocol called COOP
  • Old entries on leaf switch will be removed after 5 minutes
  • APIC is configurable through CIM-C and KVM
  • APIC will further configure the spine and leaf switches starting with IP assignment
  • Management IP offered by APIC to fabric are only for management communication and not for any outside access
  • APIC will communicate with fabric over a dedicated VRF called Overlay-1
  • VM kernel IP address subnet should be different than APIC IP assignment subnet
  • VLAN ID is required for infrastructure network 4093
  • Kernel of APIC is CENT OS
  • Cannot conf t to leaf switches

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