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ISDN Configuration

Chapter 10

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Chapter 9 2

Chapter Objectives

Explain ISDN features

Explain ISDN devices

Explain ISDN connections

Configure BRI

Configure PRI

Verify ISDN Connections

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Chapter 9 3

Recall

WAN is a network that spans a large geographical

area

Data-Link layer protocols are commonly called the

data link protocols, which communicate between two

devices

PAP is a insecure protocol because the username

and password is sent in plain text

Use debug ppp authentication to troubleshoot PPP Using CHAP protocol the server sends challenge

messages to the node. The node calculates and

sends the results back to the server

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Chapter 9 4

ISDN Features

ISDN provides Wide Area Network (WAN) services

in incremental values of 64 kbps

The features ofISDN are:

Speed

Multiple Device Support

Inexpensive

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Chapter 9 5

ISDN Channels and Services

ISDN network transmits information through the

three logical digital communication channels such as

Bearer (B) channel, Data (D) channel and Hybrid (H)

channel

H channel can be implemented as H0, H10, H11,

H12

ISDN supports two types of connections such as the

Basic Rate Interface (BRI) and Primary Rate

Interface (PRI)

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Chapter 9 6

ISDN Devices

The ISDN devices are given as follows:

Network Termination Device 1 (NT1)

Network Termination Device 2 (NT2)

ISDN Router Terminal Equipment 1 (TE1)

Terminal Equipment 2 (TE2)

Terminal Adapter (TA)

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Chapter 9 7

ISDN Connections

ISDN is a channelized service

A channelized service splits a wire into many logical

channels or time slots

Some of the common terms that are used inchannelized connections are:

Digital Signal 0 (DS0)

Digital Signal 1 (DS1)

T1 E1

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Chapter 9 8

ISDN Devices and Reference Points

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Chapter 9 9

ISDN Protocols

The following are ISDN protocols dealing with certainissues:

Protocols with E as the beginning letter deal with using

ISDN on the existing telephone lines

Protocols with I as the beginning letter deal with ISDNconcepts, aspects and services

Protocols with Q as the beginning letter deal with

switching and signaling. These protocols allow you to

connect to the ISDN and troubleshoot the network.The Q protocols include the following:

Q.921

Q.931

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Chapter 9 10

Switch Types and Connections - I

Switch Type Connection Type

basic-5ess BRI

basic-dms100 BRI

basic-ni1 BRIbasic-ni2 BRI

basic-1tr6 BRI

basic-net3 BRI

basic-nwnet3 BRI

basic-nznet3 BRI

basic-ts013 BRI

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Chapter 9 11

Switch Types and Connections - II

ntt BRI

vn2 BRI

vn3 BRI

vn4 BRI

vn5 BRI

pri-4ess PRI

pri-5ess PRI

pri-dms100 PRI

pri-nt PRI

pri-net5 PRI

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Chapter 9 12

Selecting Router ISDN Interface

To select a Cisco router with the correct ISDN

interface:

Check whether the router supports ISDN BRI

Identify the NT1 provider. NT1 ends the local loopto the Central Office (CO) of the service provider

Check whetherNT1 is Customer Premises

Equipment (CPE)

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Chapter 9 13

ISDN Call Setup Procedure

To set up an ISDN call between the router and the

ISDN switch, the D channel is used whereas,

between the switches within the service providers

network, Signaling System 7 (SS7) is used

By default, the D channel is always enabled

During the ISDN call, the calling host sends a call

setup request

Before the actual connection is established, manydifferent messages are sent across such as

progress messages and alert messages

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Chapter 9 14

Configuring BRI

You can configure the BRI for the router after

connecting the ISDN equipment

The generic steps to configure BRI are:

Setting an user name and password

Setting the switch type

Configuring ISDN interface on a router

Setting the Service Profile Identifier (SPID)

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Chapter 9 15

Setting the SPID

Service Profile IDentifier (SPID) is a set of numbers

for BRI connections that have a National ISDN-1 or

Nortel DMS-100 switch

The SPID consists of the ten-digit telephone number

for the connection and extra identification digits

The SPIDs are provided along with the switch carrier

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Chapter 9 16

Configuring PRI - I

You need to configure additional parameters for PRIon your router

After setting the switch type, you need to configure

the T1/E1 controller card and the serial interface of

the controller card The different configuration settings for the controller

card include:

Framing

Line code

Clock source

Timeslots

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Chapter 9 17

Configuring PRI - II

The generic steps to configure PRI are:

Setting the ISDN switch type with which the router

will communicate

Selecting the controller and specifying the type(T1/E1), framing type and line coding for the

provider

Setting the port to function as PRI and specifying

the PRI

slot for T1 or E1 and the speed

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Chapter 9 18

Verifying ISDN Connections

After configuring the interfaces, you need to verify

that they have been configured properly

You can verify the ISDN connections using two

commands

show interface command

show isdn status command

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Chapter 9 19

ISDN Verification Commands - I

Command Description

ping and telnet Enables you to ping or telnet the remote router

when the link is established without

considering the interesting traffic listshow dialer Provides dialer information that includes status

of the link, idle time, length of the call, router to

which the interface is connected

show isdn active Displays the phone number and whether the

call is active

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Chapter 9 20

ISDN Verification Commands - II

show isdn status Displays the detailed status of the ISDN

interfaces

show ip route Displays all the routes of the router

debug isdn q921 Enables you to view layer 2 information

debug isdn q931 Enables you to view layer 3 information

debug dialer Provides the call setup and disabled activities

isdn disconnect interface bri 0 Enables you to clear the interface and

disconnect the connection

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Chapter 9 21

Dial on Demand Routing

Cisco provides Dial on Demand Routing (DDR)

feature that allows the Cisco router to dial an ISDN

when it receives an interesting traffic

The interesting traffic is referred as IP traffic fulfilling

specific criteria such as particular protocol and

highly secured destination address

If a traffic using particular criterion is set as

interesting traffic, the traffic is given the highest

priority during the transmission

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Chapter 9 22

Making a phone connection - I

To make a phone connection, the DDR goes through the

following process:

When a packet is received, the router checks the

routing table to locate the destination

The router determines if the packet is interesting.

The router establishes DDR connection by dialing the

ISDN. When the received packet is interesting and the

DDR is not active, the router makes a phone call to

establish connection. If the received packet is notinteresting and the DDR is not active, the router drops

the packet. However, the router transmits all the

packets if the DDR already active

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Chapter 9 23

Making a phone connection - II

Once the connection is established, the router

transmits the packets from the DDR interface

The router terminates the connection if no packets

are to be transmitted or the connection remains

idle for certain period

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Chapter 9 24

DDR Configuration - I

You can allow the Cisco router to perform the DDR

process by configuring it

DDR can be used in the following situations:

The telecommuters need to connect to thecompany network periodically

There are offices that need to send transactions

or requests to the main computer at the central

office

The users need to retrieve the e-mail from the ISP

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Chapter 9 25

DDR Configuration - II

The generic steps to configure legacy DDR are:

Configuring static routes that are the routes for

remote networks

Specifying which traffic is interesting

Activating dialer list that contains the information

about the traffic that can generate calls

Configuring a dialer map that informs the router to

make a call using legacy DDR

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Chapter 9 26

Configuring Static Routes

The DDR feature of Cisco allows you to prevent

unwanted traffic from making phone calls and

keeping the line busy

configuring static routes helps in avoiding other

traffic to trigger calls

The ip route command enables you to define the

static route. The syntax of this command is:

ip route network_IP_address_# subnet_mask

remote_routers_IP_address|router_interface

[administrative_distance]

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Chapter 9 27

Specifying Interesting Traffic

Access Lists (ACLs) allows you to specify the

interesting traffic on the router

Using the dialer-list command, you can allow only

the IP traffic to establish connection

The dialer-list command enables you to specify

which traffic is interesting. The syntax of this

command is:

dialer-list [list_#] protocol [protocol_name]

permit|deny access-list [ACL_#]

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Chapter 9 28

Activating Dialer List

You need to activate the dialer list on the DDR

interface after the list is created

It is necessary to activate the list because the list is

not an ACL and it only specifies which traffic is

interesting traffic by referring an ACL

To activate the dialer list, you should use the dialer-

group command. The syntax of this command is

given as follows:

dialer-group dialer_list_#

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Chapter 9 29

Configuring Dialer Maps

Once you finish specifying the interesting traffic and

activating the dialer list on the DDR interface, you

can specify dialer information to the router

The dialer map command gives dialer information

for the router to make phone calls. The syntax of the

command is:

dialer map protocol_name

destination_router_address name [remote_router]

speed [56|64] [broadcast]

[destination_phone_number]

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Chapter 9 30

Dialer Profiles

With the help of dialer profiles, the following tasks

can be performed:

Configuring B channels with different IP subnets

Using encapsulation on the B channel Setting DDR parameters for the B channels

Eliminating the garbage ofISDN B channels by

allowing ISDN BRI interfaces to associate with

multiple dialer pools

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Chapter 9 31

Configuring Dialer Profiles

You can configure many dialer interfaces on the

router wherein each interface will contain complete

information about the possible destinations

The initial steps in configuring dialer profiles include

configuring static routes and dialer list similar to

legacy DDR

you need to configure the dialer and the physical

interfaces then

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Chapter 9 32

Verifying DDR Configuration

After configuring the interfaces, you need to verify

that they have been configured properly

To verify the DDR configuration, there are three

commands:

show dialer interface

show isdn active

show isdn status

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Chapter 9 33

Troubleshooting ISDN DDR

The show and debug commands enable you to

verify and troubleshoot the DDR connections

show command - You can use the show dialer

command to view the DDR interfaces that made

the phone calls

debug command - You can use the debug dialer

command to view the DDR process to enable or

disable the connection

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Chapter 9 34

Case Study

The Blue Diamond Steel company opened a new

branch at Hyderabad. The organization uses regular

telephone line for data transmission. All the

departments of the Hyderabad branch send the

details of their daily transactions to the Gujaratbranch. The files that contain the transaction details

are very large in size.

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Chapter 9 36

Suggested Solution

Implement Cisco routers in the network and configure

ISDN on each router. The Cisco routers provide Dial

on Demand Routing (DDR) feature, which allows the

router to call the ISDN when it receives important

traffic. Setup the PRI service for data transmission,which provides 23 B channels and 1 D channel

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Chapter 9 38

Summary - II

Network Termination Device 2 (NT2) communicates

with the ISDN protocols

ISDN Router enables multiple computers on a LAN to

share a single ISDN BRI connection

Terminal Adapter (TA) converts some other form of

signaling to ISDN to enable non-ISDN devices, such

as the TE2 to work the 2-wire ISDN network

The U point is a 2-wire interface for connecting to the

(NT1)

The division of the wire into logical time slots is termed

as Time Division Multiplexing (TDM)

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Chapter 9 39

Summary - III

The S reference point provides a 4-wire interface

between the NT1 and the ISDN networking equipment

such as an ISDN adapter or a router

Basic Rate Interface (BRI) consists of two B channels

and one D channel

Primary Rate Interface (PRI) consists of multiple B and

D channels

The ISDN interfaces can be configured using the

interface command

The Internet Service Provider (ISP) provides the

switch type for the ISDN connection

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Chapter 9 40

Summary - IV

Service Profile IDentifier (SPID) is a set of numbers

for BRI connections that have a National ISDN-1 or

Nortel DMS-100 switch

The show interface command enables you to viewthe ISDN interface configuration

The show isdn status command enables you to view

the detailed status of the ISDN interfaces