Routing design in enterprise networks is often highly complicated due to the need to accommodate various operational demands, including security, performance, and fault tolerance. This high complexity often makes the networks challenging to manage and evolve over time. Despite its significant impact, there has been limited research on systematically analyzing or addressing this complexity. This paper aims to bridge the gap by examining key aspects of enterprise routing design, identifying their inherent complexity, and linking this complexity to the underlying design requirements. By centering our analysis on the design itself— rather than vendor-specific device configurations— our approach directly exposes and models the complexity inherent to the network design. As a case study, we applied this methodology to the routing redesign of a campus network. The results demonstrate its effectiveness in tracing complexity back to design choices, connecting requirements, design, and implementation, and uncovering the root causes of excessive network complexity.