Besides having a basic understanding of network architecture/design/planning....it's always good to understand what the internal or external customer is really looking for, especially when it comes to the cost of these networks. Commercially, it may differ quite a bit if you are going with a choice of one vendor over another. Also you will need to know how to build redundancies, which are important for mission-critical use cases.
Best of luck for your career choice. i must say being involved in Networks & Telecommunications was one of my best choices in life.