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ISDN. Semester 4, Chapter 5. Table of Contents. Go There!. ISDN & The OSI Model. Go There!. ISDN Common Uses. Go There!. Configuring ISDN. Go There!. Dial-On-Demand Routing. ISDN & The OSI Model. Table of Contents. End Slide Show. What is ISDN?. - PowerPoint PPT Presentation
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ISDNISDNSemester 4, Chapter 5
Table of ContentsTable of Contents
ISDN & The OSI Model
ISDN Common Uses
Configuring ISDN
Dial-On-Demand Routing
Go There!Go There!
Go There!Go There!
Go There!Go There!
Go There!Go There!
End Slide ShowEnd Slide Show
Table of ContentsTable of Contents
ISDN & The OSI ModelISDN & The OSI Model
What is ISDN?What is ISDN? Integrated Services Digital Networks allow digital
signals to be transmitted over existing phone lines. Provides connectivity for remote sites without the
added expense of a leased line (e.g. T1) ISDN has the following benefits:
Can carry voice, video, and data on B Channel Faster call setup than modems (sometimes < 1 sec.) using
the out-of-band D (or Delta) channel Offers faster data transfer using the B (or Bearer) channels
at 64kbps (2B+D=144kbps)
BRI versus PRIBRI versus PRI Basic Rate Interface ISDN uses 2 Bearer channels at 64kbps
ea. & a 16 kbps Delta channel for signaling.(2B+D)Users get 128kbps although the link is really 144kbps plusWhen not using voice communications, both B channels are
available for data.
Primary Rate Interface ISDN uses 23 Bearer channels at 64kbps ea. & a 64kbps Delta channel for signalingAlso called a digital T1 because the total bandwidth is 1.544Mbps
Basic ISDN ComponentsBasic ISDN Components The capabilities of Customer Premise Equipment
varies. Therefore, different types of equipment exist to
provide virtually any user the ability to access the ISDN local loop.
Two questions to ask when determining the needed equipment: Does my current equipment support ISDN? Do I need to attach multiple devices to a single ISDN
connection? With those two questions in mind, let’s investigate
the options.
Basic ISDN ComponentsBasic ISDN ComponentsIs device ISDN compatible? “Yes, my device is compatible with ISDN.”
Then you have a Terminal Equipment Type 1 device (TE1)“No, my device is not compatible with ISDN.”
Then you have a Terminal Equipment Type 2 device (TE2) and will require a Terminal Adapter (TA) to convert the electrical signals to ISDN
Connect multiple devices or a single device?“No, I’m only connecting my computer.”
Then you only need a Network Termination 1 (NT1) to convert the 2-wire incoming phone line to 4-wire
“Yes, I’m connecting multiple devices.”Then you also need a Network Termination 2 (NT2) to provide switching functions
before attaching to the NT1.With the answers in mind, let’s look at a graphic.
Basic ISDN ComponentsBasic ISDN Components Notice, we’re using a NT2 to connect all devices to the NT1 The NT1 is used to terminate the BRI local loop at the
customer premise & convert 2-wire to 4-wire. Notice also that the
TE2 must have a TA since it is not compatible with ISDN.
The Reference Points (R,S,T,U) define the interface for connecting between the different devices.
S interface
T interface
BRI Local Loop
ISDN reference pointsISDN reference points
Cisco Cisco InterfacesInterfaces
In the United States, the customer is required to provide the NT1.
In Europe and various other countries, the telephone company provides the NT1 function and presents an S/T interface to the customer.
S/T interface requires an NT1 connection.
BRI S/T Interface – Cisco 2503BRI S/T Interface – Cisco 2503
Configuring ISDN interfaceConfiguring ISDN interfaceRouter(config)#interface bri numberRouter(config-if)#
If the router is a TE2 device, which does not have a native BRI, it must use an external ISDN terminal adapter.
On a TE2 router, configure the appropriate serial interface to send the ISDN traffic to the TA.
Terminal Adapter
ISDN Switches & SPIDsISDN Switches & SPIDs You must configure the router for the switch type
your provider is using for ISDN service (Similar to configuring dial-up service for the right modem).
In addition, you must know the Service Profile Identifier (SPID) your ISP is using to identify you and configure your line.
SPIDs vary in length depending on the provider. They are usually some combination of the phone number and optional numbers
For example: Phone Number: (510) 555-1234SPID: 51055512340001
ISDN EncapsulationsISDN Encapsulations If you do not configure a data link layer
encapsulation, ISDN will use the default HDLC. However, PPP is the preferred method of
encapsulating across ISDN links because… PAP/CHAP Authentication Link quality determination through LCPs and other options available through PPP
ISDN Common UsesISDN Common Uses
End Slide ShowEnd Slide Show
Table of ContentsTable of Contents
Common Uses for ISDN: SOHOCommon Uses for ISDN: SOHO Some of the characteristics of ISDN SOHOs include:
Support a limited number of simultaneous usersUse DHCP or NAT so only one outside IP address is neededSave the cost of using dedicate connections such as a T1 by only
using dialup connections.
Configuring ISDNConfiguring ISDN
End Slide ShowEnd Slide Show
Table of ContentsTable of Contents
Summary of Configuration TasksSummary of Configuration Tasks The following assumes all normal global and
interface configuration is complete. Global: Router(config)#
Select your ISP’s switch type Specify traffic to trigger DDR calls (“interesting traffic”)
Interface: Router(config-if)# Select interface specifications Configure ISDN addressing
Optional Configurations
Global: Switch TypeGlobal: Switch Type Since switch signaling differs across switch types,
you must specify the switch type Our Adtran unit is a “basic-ni” (There are about 10
switch types.) Use the command isdn switch-type nnnn
Router#config tRouter(config)#isdn switch-type basic-ni!!This command can also be entered on the interface!Router(config)#int bri0Router(config-if)#isdn switch-type basic-ni
Interface: SPIDsInterface: SPIDs SPIDs allow multiple ISDN devices, such as voice
and data, to share the local loop. . SPIDs are obtained from your service provider.
To keep them simple, SPIDs are usually some combination of the phone number plus some optional numbers (and a Local Directory Number [LDN], if necessary)
The SPID commands for each B channel are:Router(config-if)#isdn spid1 spid-number [ldn]Router(config-if)#isdn spid2 spid-number [ldn]
Router(config)#int bri0Router(config-if)#isdn spid1 51055512340001 5551234Router(config-if)#isdn spid2 51055512350001 5551235
Interface: EncapsulationInterface: Encapsulation PPP is, by far, the most favored of the encapsulations
on ISDN links because of its capabilities. Since HDLC is on by default, you must configure PPP The configuration steps are the same as we studied in
Ch. 4 – PPP. NOTE: The username name password password
command must be entered in global configuration mode in order to make CHAP authenticate.
Router(config-if)#encap pppRouter(config-if)#ppp authentication chap
Dial-On-Demand RoutingDial-On-Demand Routing
End Slide ShowEnd Slide Show
Table of ContentsTable of Contents
DDR OverviewDDR Overview A major benefit of using an ISDN link instead of a dedicated
link is its significant savings in bandwidth costs. Connections are initiated by remote offices and
telecommuters on an as-needed basis. Since the call setup time is significantly reduced compared to
traditional analog modems, the user rarely experiences a delay.
When services are no longer needed (the user times out), the call is terminated.
However, interesting traffic must be defined and filtered. Otherwise, unexpected protocols (e.g. routing updates) could cause the router to dial continuously even when the network is not in use.
DDR ConfigurationDDR Configuration Four steps:
Define what is “interesting traffic” Assign interesting traffic definition to ISDN Define destination Define call parameters
DDR: Interesting TrafficDDR: Interesting Traffic Defining “interesting traffic” involves specifying
what types of packets will initiate a call. Use the dialer-list command in global
configuration mode. The command structure, similar to ACLs, is as
follows:dialer-list dialer-group-number protocol
protocol-name {permit | deny} For example, you want IP traffic to initiate calls.Router(config)#dialer-list 1 protocol ip permit
DDR: Interesting TrafficDDR: Interesting Traffic The simple form of the dialer-list command specifies
whether a whole protocol suite, such as IP is permitted to trigger a call.
The more complex form of the command references an access list, allowing finer control of the definition of interesting traffic.
When a dialer-list command is used in conjunction with the access list, the access-list command specifies interesting traffic that initiates a DDR call.
By referencing an access list to specify interesting traffic , you have granular control of which protocols, sources, and destinations are worthy of bringing up a link.
DDR: Defining Interesting TrafficDDR: Defining Interesting Traffic
Router(config) dialer-list dialer-group list access-list-number .
The following configuration commands permits a single host to initiate DDR: RTA(config) access-list 24 permit host 192.168.1.2 RTA(config) dialer-list 1 list 24
DDR: Assign Interesting TrafficDDR: Assign Interesting Traffic Once the dialer-list is created, it needs to be
assigned to the interface responsible for initiating the call.
The command structure is:dialer-group dialer-group-number
Router(config)#int bri0Router(config-if)dialer-group 1
DDR: Define DestinationDDR: Define Destination Now configure the interface with all the parameters necessary
to reach the destination With the dialer-map command, we are “mapping” (or bundling)
Layer 3 addressing with Layer 2 addressing. In our example:
Layer 3: IP address Layer 2: LDN
The command structure is:Router(config-if)#dialer map protocol next-hop-address [name hostname] dial-string
dial-string is the ldn of the next hop address [name hostname] is the hostname of the connected router
Router(config-if)dialer map ip 172.16.20.1 name Lab-A 5551234
ISDN And Static RoutesISDN And Static Routes
Multi dialer Maps on a DDR InterfaceMulti dialer Maps on a DDR Interface
Central Office
SOHO1
SOHO2
SOHO3
ISDN Cloud
172.10.10.0/24
172.10.11.0/24
172.10.12.0/24
Ip route 172.10.10.0 255.255.255.0 10.1.1.2 Ip route 172.10.11.0 255.255.255.0 10.1.1.3 Ip route 172.10.12.0 255.255.255.0 10.1.1.4 Dialer map ip 10.1.1.2 name SOHO1 5551212 Dialer map ip 10.1.1.3 name SOHO2 5551213 Dialer map ip 10.1.1.4 name SOHO3 5551214
Setting Default/Static RoutesSetting Default/Static Routes
DDR: Passive Interface/Static RoutesDDR: Passive Interface/Static Routes When configuring your routing protocol, you want to stop
routing updates from going across your ISDN link. Why? However in order to connect to networks beyond the next
hop network, you must enter a static route.
Using ACLs To Prevent RIP From Bringing Using ACLs To Prevent RIP From Bringing Up a DDR InterfaceUp a DDR Interface
The following configuration is done at the Central Router end: (config)# access list 101 deny udp any any eq rip (config)#access list 101 permit ip any any (config) dialer-list 1 list 101 (config)#int bri0 (config-if) dialer group 1
Defining Optional Call ParametersDefining Optional Call Parameters Dial-up connections are subject to an idle timer, which
keeps track of how much time has passed since interesting traffic was routed out the interface. By default, the idle-timeout is set to 120 seconds. Router(config-if)#dialer idle-timeout seconds
When the router is waiting to use a line to make another call, it uses a more aggressive idle timeout called fast-idle. The fast-idle time is the number of seconds that a line can remain idle before the current call is disconnected to allow another call that is waiting to use the line. Router(config-if)#dialer idle-timeout 60
Router(config-if)#dialer fast-idle 15
Defining Optional Call ParametersDefining Optional Call Parameters The dialer load-threshold command is used to specify the
interface load at which the router will initiate another call to the destination. This command is typically used with Multi-link PPP
Multi Link PPPMulti Link PPP MLP provides the following: load balancing over multiple WAN links Packet fragmentation, proper sequencing Load calculation on both inbound and outbound traffic
Configuring The BRI Interface To Forward Configuring The BRI Interface To Forward Incoming Voice CallsIncoming Voice Calls
(config-if) ISDN incoming-voice modem Switch to dial-peer sub configuration mode:
Dial-peer voice 1 pots (config-dial-peer) port 1 (config-dial-peer) destination-pattern 5551234
Verifying ISDN OperationVerifying ISDN Operation To confirm ISDN is up and running, use the
command show isdn status To see an ISDN call in progress and the number
called…. First, ping the destination to activate the link. Then, use the command show isdn active to see
information about the call
Verifying ISDN OperationVerifying ISDN Operation
#show int bri 0 Spoofing is necessary because the router removes a route from it
routing table if the route points to a "down" interface.
Show ISDN StatusShow ISDN Status Command Command This command displays ISDN status information for Layer
1, Layer 2, and Layer 3.
Verifying PPP MultilinkVerifying PPP MultilinkAs soon as you configure a BRI interface with the ppp
multilink command, the router will create a virtual interface called a virtual access interface
Verifying PPP MultilinkVerifying PPP Multilink
The output of this command displays which links are members of the bundle
Verifying PPP MultilinkVerifying PPP Multilink
The debug dialer command indicates whether the multilink is up after authentication, and also indicates when the overload occurs.
The debug ppp multilink command displays packet sequence numbers. It is useful only as a last resort because it does not help troubleshoot when connections are not being bundled.
ISDN Debug CommandsISDN Debug Commands
Identification Identification RequestRequest
Identification Identification AssignmentAssignmentAction Action
IndicatorIndicator
Set Asynchronous Set Asynchronous Balanced Mode Balanced Mode
ExtendedExtended
ISDN Debug CommandsISDN Debug Commands
ISDN LabsISDN Labs