Configuring a T1/E1 CSS Interface

controlcontrol Member Posts: 309
Reading through the above in the Cisco Press book and it states the following...

"After you enter the pri-group command, the router creates 24 ISDN voice ports that it will use for incoming and outgoing voice calls. This is verified with the show voice port summary command. Notice that the voice port is labeled with the identifier 1/ 0: 23. This represents channel 23 (time slot 24) of the T1 ISDN PRI connection (channels are listed from 0– 23, whereas time slots are listed 1– 24 which is the dedicated signaling channel used to bring up the other 23 voice bearer channels"

My question is, if channel 23 is the dedicated signalling channel as stated above, does this mean there will only be 23 ports available for incoming/outgoing voice, as 1 port is used for signalling? OR is this a temporary "signal" to bring up the other bearer channels? Not sure if I'm understanding the statement from the book so please correct me.


  • azaghulazaghul Member Posts: 569 ■■■■□□□□□□
    The command pri-group timeslots 1-24 will create 23 B channels (0-22) and the 1 D channel (23).

    The D channel is permanent, leaving 23 channels for bearer traffic, and will appear as int serial x/y/z:23 and voice-port x/y/z:23 in the running config, and is used for stream clocking and B channel signalling.
  • thsouthernthsouthern Member Posts: 9 ■□□□□□□□□□
    card type e1 2
    isdn switch-type primary-net5
    voice-card 0
    no dspfarm
    controller E1 0/2/0
    pri-group timeslots 1-17
    description --- Inbound E1 interface ---
    controller E1 0/2/1
    pri-group timeslots 1-17
    description --- Outbound E1 interface ---
    controller E1 2/0
    pri-group timeslots 1-31
    description ISDN/PRI E1 - TelecomAsia
    vlan internal allocation policy ascending
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