The IP telephony Cookbook is a reference document addressing technical issues for the set-up of IP telephony solutions. Its goal is to provide the TERENA user community with guidelines and information about the IP telephony world and everything related with it. Since the Cookbook is intended to be a technical document, the main target audience addressed here are the network engineers and system administrations at universities and National REsearch Networks (NRENs); however, university students and researchers may found it useful both for having a technology background and for finding in it information about advanced research topics and projects in the european community.