Virtual Private Networks, 2nd Edition (O'Reilly Nutshell)
Mike Erwin, Charlie Scott, Paul Wolfe
I didn't check out the publication date of this book when I bought it (1998) so my dissapointment is partly my fault. It is, unsuprisingly, very outdated (anyone actually remember the altavista tunnel?). However, much of the info that remains, even general VPN fundamentals, are flawed and innacurate. This book will hinder you if you are trying to understand proper VPN network topologies.
