Overview
Even if your network starts with two routers and a link, it's never too early to begin planning how your internetwork will look as it grows. You also need to think about network design because of increasing connectivity demands and the phenomenal growth of today's internetworks. In order to meet these growth requirements, the internetworks you design and build must be scalable. Scalable internetworks are typically described as flexible and expandable networks that are experiencing constant growth and that can be adjusted without major modification.

In this chapter, you will learn about hierarchical design principles for building scalable internetworks and you will learn how routers can provide the critical elements required to build scalable internetworks by offering varying levels of connectivity for workgroups and critical networks, such as a backbone network. In addition, you will be introduced to key characteristics for building a secure, responsive, and adaptable internetwork.