Skip to content

3-Stage Clos Example#

Overview#

  • A 3-stage Clos and a 5-stage Clos are provided as examples. These designs provide the basic concepts and can be extended if needed.
  • For simplicity, both examples are built with 7220-IXR-D series switches which are built on the Trident3 chipset.
  • These examples are not exhaustive. There are many different ways to build Clos networks depending on the design goals.

Network Diagram#

3-stage Clos

Assumptions#

  • Uplinks from Leaf to Spine are 100G
  • Servers can connect at either 10G or 25G
  • Support for single-homed or dual-homed servers (only impact is server density)
  • Oversubscription calculations are based on 25G downlink and 100G uplink
    • Ratio could change by adding more Spines (up to 8 max)
  • Connections out of the fabric will come via a pair of Leaf nodes (Border Leafs)
  • Oversubscription ratio is 1:1 between Spine and Border Leaf

Details#
Spine node 7220-IXR-D3 (32xQSFP28 + 2xSFP+)
Leaf node 7220-IXR-D2 (48xSFP28+8xQSFP28)
Border Leaf node 7220-IXR-D3 (32xQSFP28 + 2xSFP+)
# of Spines 4
# of Leafs 30
# of Border Leafs 2
Max single-homed servers 1,440 (48*30)
Max dual-homed servers 720 (48*15)
Leaf-to-spine oversubscription 3:1