Michael Coker & Erik Freeland 
DCN: Designing Cisco Networks [PDF ebook] 

The demand for certified networking professionals that have experience with Cisco(R) products and Cisco-based networks has never been higher. Written in conjunction with CCprep.com, the premier Cisco certification training Website, DCN: Designing Cisco(R) Networks gives you full, curriculum-based coverage to help you study for the CCDA exam and succeed as a Cisco professional. Comprehensive, thorough, and reliable, this is the only book you’ll need for both preparing for the CCDA exam, and as a helpful on-the-job desk reference.