Venture into any bookstore today and you can find numerous books on internetworking covering a wide
range of topics from protocols to network design techniques. There's no question that internetworking has
become a popular field with the enormous growth of the Internet and the increasing convergence of voice,
video, and data. Cisco has built a very successful business selling the equipment that forms the network
infrastructure—by some accounts, Cisco has more than 85 percent of the market—and at the same time
has seen its Cisco IOS Software become a de facto industry standard. Yet, although plenty of material is
written about network design and the protocols IOS supports, very little information is available from
sources other than Cisco.
This lack of information is understandable—IOS is proprietary, after all—but it nevertheless leaves network
implementers at a disadvantage. During our experience helping design and troubleshoot IOS-based
networks, we've seen many cases where limited IOS architectural knowledge either contributed to a
problem or made it more difficult to solve. In addition, we collectively have answered countless numbers of
questions (and dispelled some myths) from bewildered Cisco customers about the workings of various IOS
features.
This book is an attempt to bring together, in one place, the wealth of information about the architecture and
the operation of IOS. Some of this information has been made public previously through forums, Cisco
presentations, and the Cisco Technical Assistance Center. Most of the information you cannot find in the
Cisco IOS documentation.