408 Chapter A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
12
Which command, used with callback, ensures that a callback is made only to a properly
configured client?
dialer callback-secure
13
What command informs a router that it is to be a callback client?
ppp callback request
14
What command informs a router that it is to be a callback server?
ppp callback accept
15
What is the default time interval between CHAP challenges?
Two minutes
16
In the event of PPP authentication failure, what happens to the call?
The call is immediately disconnected.
Answers to Chapter 6 "Do I Know This Already?" Quiz
1
List the two most common implementations of ISDN.
The two most common implementations of ISDN are BRI and PRI.
2
List the number of bearer channels for BRI, T1 PRI, and E1 PRI.
The numbers are BRI = 2, T1 PRI = 23, and E1 PRI = 30.
3
What type of information is carried over the D channel?
Signaling (and sometimes data, depending on the implementation) is carried over the D
channel.
4
List the specifications that define Layer 2 and Layer 3 of ISDN.
The specifications are Layer 2 = Q.921 and Layer 3 = Q.931.
5
When is it necessary to use dialer in-band in an ISDN BRI configuration?
When the router does not have a native BRI interface, a terminal adapter must be placed
between it and the NT1. The dialer in-band command must be used to utilize bandwidth
from each B channel for signaling.
6
What is the difference between a router with a BRI S/T interface and one with a BRI U
interface?
BRI S/T interfaces do not have an integrated NT1, whereas BRI U interfaces do include
an integrated NT1.