AI training and distributed storage are pushing data center single-port bandwidth from 100G to 400G. Directly tearing down and rebuilding will waste existing investment and disrupt business. A more reliable way is to perform evolutionary upgrades on the existing Spine-Leaf architecture. This article breaks down the steps that can be implemented.

First determine whether you really need 400G

400G is not suitable for all computer rooms. It is only worthwhile to upgrade to 400G when the Leaf uplink continues to be fully loaded during business peaks and a single 100G port becomes a clear bottleneck, or the GPU cluster aggregation bandwidth is insufficient and parameters are queued for synchronization. In other scenarios, the pressure can be relieved by increasing the number of uplinks and reducing the convergence ratio, and the cost is often lower.

The evolution path from coarse to fine

  • Step 1: Change the Spine-Leaf uplink from 100G to 400G. Keep the access layer unchanged at 25G/100G. Resolve the backbone bottleneck first.
  • Step 2: Check the link's loss budget and optical fiber reach. For long distances between buildings, the actual luminous margin must be measured. It is recommended to leave about 3dB.
  • Step 3: Depending on the traffic, upgrade the high-load server access to 400G, and cut over the connections in batches to avoid simultaneous activation.

Packaging and wiring compatibility points

400G commonly uses QSFP-DD and other packages. When migrating from 100G QSFP28, you should pay attention to the compatibility of the switch cage and the backplane. Please confirm with the equipment manufacturer before mixing. Transition section inside the cabinet is available40G AOC active optical cableCombined with DAC; refer to the renovation of the main trunk between buildings100G optical fiber interconnection upgrade between buildings in a large data center in East ChinaActual test experience, jumpers are usedLC-LC 10G multi-mode OM3 two-core jumperWaiting for mature specifications.

The pace of evolution must leave panel and power supply margin for the next generation speed. EB-LINK can provide high-speed module coding and unit-by-unit testing. For transition plans, please contact 0755-83179002.