Plan a 40G to 100G migration: ports needed, capacity gain and access ports gained through 4×25G breakout.
The migration is sized on projected demand rather than a port-for-port swap, because each 100G port carries two and a half times the traffic of a 40G port and therefore fewer ports are needed. Where the workload is 10G or 25G servers, breakout turns each 100G port into four access ports and avoids buying separate access switches. 40G uses four 10G lanes and is a technological dead end; 25G-based 100G is cheaper per gigabit and is the step that unlocks 400G later on the same fibre.
40G to 100G Migration
projected demand = 40G ports × 40 × utilisation × (1 + growth); 100G ports = ceil(demand ÷ 100); each port carries 2.5× more, so the gain per port is 150%.
projected demand = 40G ports × 40 × utilisation × (1 + growth); 100G ports = ceil(demand ÷ 100); each port carries 2.5× more, so the gain per port is 150%. The migration is sized on projected demand rather than a port-for-port swap, because each 100G port carries two and a half times the traffic of a 40G port and therefore fewer ports are needed. Where the workload is 10G or 25G servers, breakout turns each 100G port into four access ports and avoids buying separate access switches.
40G uses four 10G lanes and is a technological dead end; 25G-based 100G is cheaper per gigabit and is the step that unlocks 400G later on the same fibre.
This calculator takes 4 inputs: 40G ports in service, Average utilisation today, Growth over the planning horizon, Use 100G to 4×25G breakout for access. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.