Umer Khan`s first book, Cisco Security Specialist`s Guide to PIX Firewalls, ISBN: 1931836639, has consistently maintained its spot as the #1 bestselling PIX book on amazon.com by providing readers with a clear, comprehensive, and independent introduction to PIX Firewall configuration. With the market for PIX Firewalls maintaining double digit growth and several major enhancements to both the PIX Firewall and VPN Client product lines, this book will have enormous appeal with the audience already familiar with his first book.