Truly the don. So long as you don't need BGP (covered in vol II & Halabi's BGP bible) then this rocks. Section 1 covers the basics, and well. Section 2 is a fairly exhaustive guide to IGP protocols which is not bettered anywhere. Although the ISIS chapter lacks a little in the way of fine-tuning tips its still the best I've seen and the other sections most relevant nowadays (OSPF, RIP2, EIGRP) are also great. The detail required for CCIE prep and effective understanding for large-scale network design and troubleshooting is all here. Section III is a vital guide to the nuances of policy-based routing and route-redistribution. Aside from MPLS, along with vol II this provides the bomdiggy of routing reference.