Within a more and more complex environment, where connectivity, reactivity and availability are mandatory, companies must be “electronically accessible and visible” (i.e., connection to the Web, e-mail exchanges, data sharing with partners, etc.). As such, companies have to protect their network and, given the broad range of security solutions on the IT security market, the only efficient way for them is to design a global secured architecture. After giving the reader all the necessary materials and explaining classical security and services needs, this chapter proposes three different realistic security-level architectures that may be currently deployed within companies. For more realistic analysis and illustration, two examples of companies with different size and profile are given. A number of advices, explanations and guidelines are provided in this chapter so readers are able to adapt those architectures to their own companies and both security and network needs.