Additional Isdn Pri Configuration Parameters

This topic describes the commands that are required to configure the ISDN PRI channels and D channel. After the T1 or E1 controller is configured, the PRI channels and the corresponding D channel interface must be configured.

Additional ISDN PRI Configuration Parameters

Router(config-controller)#pri-group [timeslots range]

* Specifies ISDN PRI on the T1 or E1 controller

* Specifies timeslots (channels) used by PRI

Router(config)#interface serial {slot/port | unit:}{23 | 15}

* Specifies the serial interface for the PRI D channel

Router(config-if)#isdn incoming-voice modem

* Switches incoming analog calls to internal modems

© 2004 Cisco Systems, Inc. All rights reserved. bcran v2.1-


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 the interface serial commands that 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 DS-0s 0 to 22 as the B channels, and DS-0 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 isdn incoming-voice modem command allows incoming analog calls to be switched to internal modems. Software examines the bearer capability fields of the D channel data and determines whether a call is a normal ISDN call or an analog call being carried on an ISDN B channel. If it is an analog call, it is switched to internal modems. This command is only available for access servers with the capability for internal modems.

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