Chapter 12. Troubleshooting ISDN

Terms you'll need to understand:

• Challenge Handshake Authentication Protocol (CHAP)

• Demarcation point

• Dial-on-demand routing (DDR)

• Integrated Services Digital Network (ISDN)

• Local Loop

• Point-to-Point Protocol (PPP)

Techniques you'll need to master:

• How to configure dial-on-demand routing

• Identify frequent ISDN problems

• Understand and know how to troubleshoot CHAP

• Troubleshoot dialer mappings

• Troubleshoot PPP

• Configure and troubleshoot dialer and access lists

• Understand Layer 1 through Layer 3 and the connection process

• Understand q.921 and q.931 signaling

• Use ISDN troubleshooting show and debug commands

ISDN is one of the more difficult wide area network (WAN) protocols to understand and to configure. Most companies are using this technology less and less with the introduction of DSL technologies. ISDN is still popular in rural areas because of the distance limitations of DSL. ISDN is still an option for administrators to consider when connecting LANs together through a WAN, and communicating through multimedia technologies, such as video conferencing. The Support exam will test your knowledge of troubleshooting ISDN protocols. This chapter begins with an overview of ISDN, then discusses techniques for troubleshooting an ISDN configuration. You also learn the ISDN troubleshooting commands you will need to know ”both in your work and in preparation for the exam.

This chapter was written based on use of a Cisco 804 router. This router includes a four-port hub, as well as an ISDN/U (ISDN BRI) interface. Although this book focuses on troubleshooting, this chapter provides only a brief overview of ISDN. For a more in-depth discussion on ISDN, you should read CCNP BCRAN Exam Cram 2 , by Eric Quinn and Fred Glauser, 2003, also published by Que.