Problem-based learning (PBL) is a pedagogical method that challenges students to ''learn how to learn'' by working cooperatively in groups to develop solutions to real world problems. Network in a Box (NiB) is a unique, engineering-oriented effort to employ PBL in core computer networks curriculum.Developed as an openended exercise in PBL, NiB sets a learning environment in which student teams design and implement a network emulator using off-the-shelf hardware and open-source software. The aims of this article are twofold. The first goal of this article is to catalogue our efforts at San Diego State University in implementing PBL in a computer networks engineering course. The second goal of this article is to introduce the NiB project as a viable example of PBL in the field of computer networks. This project not only arms students with a good understanding of network impairments but also provides the knowledge of low level packet processing, packet creation, packet injection into the network, meeting real time processing requirements of packet processing and packet filtering. By arming students with an understanding of network impairments, a working knowledge of low-level packet processing, packet creation, packet injection, and their processing requirements, NiB serves as a model introduction of PBL into the field of computer networks engineering. In this article we disseminate the product specification and system design as an educational and research utility along with an assessment of this project as perceived by students over several semesters