Foundation Summary 363

Foundation Summary

The “Foundation Summary” section lists the most important facts from the chapter. Although this section does not list everything that will be on the exam, a well-prepared CCNA candidate should at a minimum know all the details in each Foundation Summary before taking the exam.

Table 10-17 lists the number of channels for BRI and PRI.

Table 10-17 BRI and PRI B and D Channels

The OSI layers correlating to the different ISDN specifications are also mentioned in the ICND course. It’s also useful to memorize the specifications listed in Table 10-18, as well as which OSI layer each specification matches.

Table 10-18 ISDN I-Series and Q-Series Mentioned in ICND: OSI Layer Comparison

Figure 10-13 shows the cabling diagram for several examples of ISDN BRI function groups and reference points.

364 Chapter 10: ISDN and Dial-on-Demand Routing

Figure 10-13 ISDN Function Groups and Reference Points

The four key concepts behind Legacy DDR are as follows:

1.Route packets out the interface to be dialed.

2.Determine the subset of the packets that trigger the dialing process.

3.Dial (signal).

4.Determine when the connection is terminated.

Table 10-19 summarizes the commands needed to configure Legacy DDR, with some explanation of each function.

Table 10-19 Summary Legacy DDR Configuration Commands

Table 10-20 summarizes the configuration details for ISDN BRI.

Table 10-20 Summary of the New Configuration Needed for ISDN BRI Beyond Legacy DDR Configuration

Table 10-21 summarizes the configuration details for ISDN PRI.

Table 10-21 Summary of the New Configuration Needed for ISDN PRI Beyond Legacy DDR Configuration

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Table 10-21 Summary of the New Configuration Needed for ISDN PRI Beyond Legacy DDR Configuration (Continued)

The configuration for dialer profiles is very similar to Legacy DDR configuration. The differences are summarized in Table 10-22.

Table 10-22 Summary of the New Configuration Needed for Dialer Profiles Versus Legacy DDR

The additional commands used with MLP in dial environments are summarized in Table 10-23.

Table 10-23 Summary of the New Configuration Needed for MLP Versus Legacy DDR

Q&A 367

Q&A

As mentioned in the Introduction, you have two choices for review questions. The following questions give you a bigger challenge than the exam because they are open-ended. By reviewing with this more-difficult question format, you can exercise your memory better and prove your conceptual and factual knowledge of the topics covered in this chapter. The answers to these questions are found in Appendix A.

For more practice with exam-like question formats, including multiple-choice questions and those using a router simulator, use the exam engine on the CD.

1.What does LAPD stand for? Is it used as the Layer 2 protocol on dialed ISDN bearer channels? If not, what is?

2.What do ISDN, BRI, and PRI stand for?

3.Define function group. List two examples of function groups.

4.Define the term reference point. Give two examples of reference points.

5.How many bearer channels are in a BRI? What about a PRI in North America? What about a PRI in Europe?

6.True or false: ISDN defines protocols that can be functionally equivalent to OSI Layers 1, 2, and 3. Explain your answer.

7.What reference points do ISDN BRI interfaces on Cisco routers use?

8.Is LAPD used on ISDN channels? If so, which ones?

9.What standards body defines ISDN protocols?

10.What ISDN functions do standards ITU-T Q.920 and Q.930 define? Does either standard correlate to an OSI layer?

11.What ISDN functions does standard ITU-T I.430 define? Does it correlate to an OSI layer?

12.What does SPID stand for? What does it mean?

13.Define TE1, TE2, and TA. Which implies that one of the other two must be in use?

14.How many B channels are there on a PRI in countries where the PRI is based on a T1? On an E1?

15.What reference point is used between the customer premises and the phone company in North America? What about in Europe?

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16.What problem does multilink PPP solve when multiple B channels have circuits set up between a pair of routers?

17.What is the syntax of an interface command used to configure the encapsulation, IP address, and DDR parameters on a PRI in North America? What is the significance of entering a colon and a number after entering the interface number?

18.What data-link (OSI Layer 2) protocols are valid on an ISDN B channel?

19.Define MLPPP. Describe the typical home or small office use of MLPPP.

20.Configure ISDN interface BRI1, assuming that it is attached to a DMS-100 ISDN switch and that it uses only one SPID of 404555121201.

21.Describe the decision process performed by the Cisco IOS software to attempt to dial a connection using Legacy DDR.

22.If packets from 10.1.1.0/24 are “interesting” in relation to DDR configuration, such that packets from 10.1.1.0/24 cause a DDR connection out interface BRI0, list the configuration commands that make the Cisco IOS software think that those packets are interesting on BRI0. (If you have not yet studied access lists, you might simply note what kind of packets you would match with an access list, rather than writing down the full syntax.)

23.Router R1 has two BRI interfaces. Configure a dialer profile such that R1 can dial any of six different remote routers using any of the B channels on either BRI. Assume that all traffic is interesting. You may ignore the static route commands needed to send the packets out the correct interface. Do not use any SPIDs, and do not use CHAP. For other parameters not listed, you can make up values.

This chapter covers the following subjects:

■Frame Relay Protocols

■Frame Relay Configuration