I'm curious,

I have a small datacenter in which I'm deploying a very flat structure (like arista's network). I have two nexus 9k's and two fex's attached. If we are to grow larger I'd like to move into more of a Leaf-spine.

I'm using traditional vlan and VRF's to segment my "production" network from my "dev" network. I do not have a need as of yet for VXlan or NSX or an overlay. I'm having issues with clos network designs that don't jump right into overlay's. I'm assuming it's because the lack of layer 2?

  • Can you be more specific? What do you mean by "issues?" VXLAN is more of a DCI technology.
    – Ron Trunk
    Sep 9 '15 at 1:58
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 12 '17 at 5:38

CLOS networks simply describe the underlying L1 topology - mainly with regards to interface over-subscription and leaf interconnection.

What you run on top of it (VLAN/VXLAN/IP Fabric) is really up to the implementation and the problem you are trying to solve.

For the network you are describing (number of switches), it sounds like a simple Fat-Tree topology would suit better


CLOS network architecture is a viable option for a scalable datacenter network. It is a good option for connecting multiple pods to each other and is ideal for optimal east-west traffic flow within your fabric

As for L2 vs L3 fabric. Layer 3 scales better and is a good option for keeping failure domains small but technologies like TRILL (e.g. Cisco FabricPath, Brocade VCS Fabric, etc.) may be used to build a non blocking L2 fabric which are easier to manage and are suitable for small size datacenter networks

If you would go for a Layer 3 CLOS architecture you would need to use overlay networking for virtual machine mobility between your leafes / pods which might complicate your design.

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