Common Channel Signaling CCS Overview of Isdn Pri Configuration Commands

Configuring ISDN PRI requires global and interface configuration commands.

Selecting the correct switch type to which to connect is crucial when configuring ISDN PRI. This topic provides an overview of the isdn switch-type command.

Pri Signaling

Use the isdn switch-type command to specify the central office PRI switch to which the router connects. With Cisco IOS® Release 11.3(3)T or later, this command is also available as a controller command to allow different switch types to be supported on different controllers. If configured as a global command, the specified switch type applies to all controllers, unless one is specifically configured on a controller.

An incompatible switch selection configuration can result in failure to make ISDN calls. After changing the switch type, you must reload the router to make the new configuration effective. Telco isdn switch-type commands are shown in the table here.

isdn switch-type Command




AT&T Primary-4ESS switches (United States)


AT&T Primary -5ESS switches (United States)


NT DMS-100 switches (North America)


National ISDN switch type


NTT ISDN PRI switches (Japan)


European and Australian ISDN PRI switches


QSIG signaling per Q.931


No switch defined

Unlike BRI operation, ISDN PRIs do not use service profile identifiers (SPIDs). Therefore, there is no requirement to configure SPIDs, regardless of the ISDN switch type used by the PRI.

Use the controller {t1 | e1} slot/port command in global configuration mode to identify the controller to be configured. Use a single unit-number to identify the AS5000 Series controller.

controller {t1 | e1} Command




Specifies the controller interface for North America and Japan.


Specifies the controller interface for Europe and most other countries in the world.

slot/port or unit number

Specifies the physical slot/port location or unit number of the controller.

Once the T1 or E1 controller is configured, the PRI channels and the corresponding D channel interface must be configured. This topic lists and explains the commands required to configure the ISDN PRI channels and D channel.

ISDN PRI Configuration Commands


pri-group timeslots range

• Sets the PRI group with a range of timeslots


interface serial slot/port:timeslot

• Sets the PRI D channel

The pri-group command configures the specified interface for PRI operation and specifies which fixed timeslots (channels) are allocated on the digital facility of the provider.

pri-group Command



timeslots range

The range of timeslots allocated to this PRI. For T1, use values in the range of 1 to 24, and for E1, use values from 1 to 31. The speed of the PRI is the aggregate of the channels assigned.

Example #1: If using all 30 B channels on an E1 PRI (30B+D), specify pri-group 1-31.

Example #2: If allocated only the first eight B channels (512 kbps total data bandwidth) for a T1 PRI (23B+D), then specify pri-group 1-8,24. Note that the D channel must be specified.

Note When provisioning a PRI line with less than 24 time slots (or 30 for E1), include the D

channel for signaling.

Specification of the PRI group automatically creates the corresponding serial interface for the D channel: interface serial {slot/port | unit}:{23 | 15}. This interface is used to configure the PRI D channel. The table shows interface serial commands you can use.

interface serial Command




The slot/port of the channelized controller.


The unit number of the channelized controller on a Cisco 4000 or AS5000 Series router.


A T1 interface that designates channelized DS0s 0 to 22 as the B channels, and DS0 23 as the D channel.


An E1 interface that designates 30 B channels and timeslot 16 as the D channel.

Note In an E1 or T1 facility, the channels start numbering at 1 (1 to 31 for E1 and 1 to 24 for T1).

Serial interfaces in the Cisco router start numbering at 0. Therefore, channel 16, the E1 signaling channel, is serial port subinterface 15. Channel 24, the T1 signaling channel, is serial subinterface 23.

The following topic highlights a sample ISDN PRI configuration.

ISDN Configuration Tasks


CMERouter(config)#isdn switch-type primary-ni CMERouter(config)#controller t1 0/1 CMERouter(config-controller)#pri-group timeslots 1-24 CMERouter(config-controller)#framing esf CMERouter(config-controller)#linecode b8zs CMERouter(config-controller)#clock source line CMERouter(config)#interface serial:23

The table describes the commands found in the figure.

PRI Configuration Commands



isdn switch-type primary-ni

Selects a switch type of National ISDN

controller t1 0/1

Selects the T1 controller 0/0.

pri-group timeslots 1-24

Establishes the interface port to function as PRI with 24 timeslots (including D channel) designated to operate at a speed of 64 kbps.

framing esf

Selects Extended Superframe (ESF) framing, a T1 configuration feature.

linecode b8zs

Selects line code B8ZS for T1.

clock source line

Specifies the T1 line as the clock source for the router.

interface serial 0/0:23

Identifies the D channel on serial interface 0/0.

The controller t1 0/1 command configures the T1 controller. In the example, the switch type selected using the national ISDN standard. This example is accurate for some operations in the United States.

For an E1 example, the timeslot argument for the pri-group command would be 1-31 rather than 1-24 as shown for a T1 example, and the interface command would be 0/1:15 instead of 0/1:23.

Dial Peers

What is Dial Peer?

This topic describes dial peers and their applications.

This topic describes dial peers and their applications.

When a call is placed, an edge device generates dialed digits as a way of signaling where the call should terminate. When these digits enter a router voice port, the router must have a way to decide whether the call can be routed, and where the call can be sent. The router does this by looking through a list of dial peers.

A dial peer is an addressable call endpoint. The address is called a destination pattern and is configured in every dial peer. Destination patterns can point to one telephone number only or to a range of telephone numbers. Destination patterns use both explicit digits and wildcard variables to define a telephone number or range of numbers.

The router uses dial peers to establish logical connections. These logical connections, known as call legs, are established in either an inbound or outbound direction.

Dial peers define the parameters for the calls that they match. For example, if a call is originating and terminating at the same site, and is not crossing through slow speed WAN links, then the call can cross the local network uncompressed and without special priority. A call that originates locally and crosses the WAN link to a remote site may require compression with a specific codec. In addition, this call may require that voice activity detection (VAD) be turned on, and will need to receive preferential treatment by specifying a higher priority level.

Cisco Systems voice-enabled routers support two types of dial peers:

■ Plain old telephone service (POTS) dial peers: Connect to a traditional telephony network, such as the public switched telephone network (PSTN) or a PBX, or to a telephony edge device, such as a telephone or fax machine. POTS dial peers perform these functions:

— Provide an address (telephone number or range of numbers) for the edge network or device

— Point to the specific voice port that connects the edge network or device

■ Voice over IP (VoIP) dial peers: Connect over a packet network. VoIP dial peers perform these functions:

— Provide a destination address (telephone number or range of numbers) for the edge device that is located across the network

— Associate the destination address with the next hop router or destination router, depending on the technology used

Cisco Public

In the figure, the telephony device connects to the Cisco Systems voice-enabled router POTS dial. The POTS dial peer configuration includes the telephone number of the telephony device and the voice port to which it is attached. The router knows where to forward incoming calls for that telephone number.

The Cisco voice-enabled router VoIP dial peer is connected to the packet network. The VoIP dial peer configuration includes the destination telephone number (or range of numbers) and the next hop or destination voice-enabled router network address.

Follow the steps to place a VoIP call:

How to Place a VoIP Call




Configure the source router with a compatible dial peer that specifies the recipient destination address


Configure the recipient router with a POTS dial peer that specifies which voice port the router uses to forward the voice call

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  • barbara
    How does common channel signaling works?
    3 years ago

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