410 Chapter A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
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 sigaling.
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.
7
Write out the commands to define only Telnet and FTP as interesting traffic for DDR.
The following commands define only Telnet and FTP as interesting traffic for DDR:
access-list 100 permit tcp any any eq 23
access-list 100 permit tcp any any eq 20
access-list 100 permit tcp any any eq 21
dialer-list 1 protocol ip list 100
8
List two of the most common encapsulations available for use on BRI interfaces.
Two of the most common encapsulations available for use on BRI interfaces are PPP and
HDLC.
9
An interface that has been configured not to send routing updates is known as what type
of interface?
The interface is a passive interface.
10
When using rotary groups, what should determine the dialer interface number?
The logical dialer interface number must match the rotary-group number defined on each
physical interface.
11
What technology is used to provide redundancy for WAN links?
Dial backup is used to provide redundancy.