ISDN and Dial on Demand Routing In terms of preparing for the CCIE lab, I feel that ISDN is probably the second most important topic to master because a significant number of points on the lab exam can come from ISDN- and DDR-related topics. It's worth remembering that ATM, ISDN, and Frame Relay were all developed as part of the same standards process, a process that followed and drew from the OSI model development. This Study Guide will attempt to address the level of ISDN and DDR knowledge needed for both the written and the lab portion of the CCIE exam. Become a ZONE Subscriber and gain access to all Study Guides Author: David Wolsefer Technical Level: CCNP™ and CCIE™ and CCIE Security & CSS1™ CCNP-Remote Access Date of Issue: 11-01-2023 Rating:   4 of 5    Table of Contents  Tutorial  3 Sample Study Questions  24 Study Questions  Lab Scenario Abstract  Lab Scenario Return to Study Guides