Years ago, the standard practice was to configure every single network device by hand. This was possible mainly because the routers and switches were routing the traffic of physical servers, so not much configuration was needed on each networking device, and changes were slow-paced. In addition, humans were the only ones to have enough information on machines to set up networking. Everything was very manual in terms of both planning and execution.
Virtualization changed this paradigm, as it has resulted in thousands of machines being connected to the same switch or router, each with potentially different networking requirements. Changes are fast-paced and expected frequently, and with virtual infrastructures defined in code, it becomes a full-time job for a human administrator to just keep up with the changes to the infrastructure. Virtualization...