An administrator needs to create a partial PRI consisting of the first seven timeslots available. Which configuration snippet configures the ISDN E1 PRI for this task?

The command pri-group timeslots 1-7 under the controller E1 0/0/0 context correctly configures a partial ISDN PRI. This command assigns the first seven available timeslots (1 through 7) as bearer channels (B-channels). For an E1 controller, the Cisco IOS operating system automatically and implicitly reserves the standard timeslot 16 for the signaling channel (D-channel). Therefore, this single line of configuration fulfills the requirement to create a partial PRI using the first seven B-channels and the default D-channel.

A. This configuration is unnecessarily explicit. The standard configuration practice is to define only the B-channels in the pri-group command, as the system defaults to timeslot 16 for the D-channel on E1 circuits.
B. The ds0-group command is used to configure Channel Associated Signaling (CAS) trunks, such as E&M wink-start, not ISDN PRI, which uses Common Channel Signaling (CCS).
D. The channel-group command is used for creating channelized T1/E1 interfaces for non-PRI applications or for T1 CAS, not for configuring an ISDN PRI group.

1. Cisco IOS Voice Command Reference, Release 15M&T: In the documentation for the pri-group command, it is stated that for E1 controllers, the D-channel is on timeslot 16 by default. Configuration examples for partial PRIs demonstrate specifying only the range of B-channels.

Source: Cisco IOS Voice Command Reference, pri-group command description. (A specific page number is not applicable for this dynamic online reference, but the information is found under the command's usage guidelines for E1 controllers).

2. Cisco IOS Voice Configuration Guide, Release 12.4: This guide provides examples for configuring ISDN PRI on E1 controllers. An example shows the configuration of a partial PRI using a command similar to the correct answer.

Source: Cisco IOS Voice Configuration Guide, Release 12.4, Chapter: "Configuring ISDN PRI," Section: "PRI for T1/E1 Configuration Task List." The example pri-group timeslots 1-10 illustrates that only the B-channel range needs to be specified.

3. Cisco Unified Communications Manager and Interoperability, Gateway Configuration: Official Cisco documentation on gateway configuration consistently shows that for a standard E1 PRI setup, the pri-group timeslots command defines the B-channels, and the D-channel at timeslot 16 is configured by default.

Source: Cisco Press, "Implementing Cisco Unified Communications Manager, Part 2 (CIPT2) Foundation Learning Guide: (CCNP Voice CIPT2 642-457)", Chapter 3, "Gateway and Trunk Configuration", Section "Configuring an E1 PRI". This section explains the implicit assignment of the D-channel.