Capex vs Opex – Hidden complexity by making an unmanageable network
Many networking solutions purport great Opex savings through automation, simulation and continuous integration. Similarly, there is a school of thought where network designs will have a single point in a network perform multiple roles. This will short change an initial Capex cost of purchasing additional switches with the intention of overlapping features on that single device.
Let’s take the simplest example. We have a 3 rack environment with dual-leaf per rack and 2 spines for inter-rack connectivity. In this design, we are leveraging VXLAN as the data plane overlay with BGP/EVPN as the control plane. Additionally, all 3 racks are compute, leaving no additional leafs to act as the service/border/exit leafs.

A network designer will look at the infrastructure and try to overlap features by repurposing the spines as exit leafs. Why will they think this way, you ask? Well, this is only an 8 switch design. Spending money on an additional 2 switches to act as dedicated border leafs uplifts my capex cost by 25 percent! I would then be required to buy 10 total switches instead of 8.

So instead, we end up overlaying the VXLAN onto the spines. So now the spines act as both interconnections between Continue reading








