Cisco AS5350XM Configuration Manual page 82

Configuring the D Channels for ISDN Signaling
Configuring the D Channels for ISDN Signaling
The ISDN D channels carry the control and signaling information for your ISDN calls—for both
circuit-switched data calls, and analog modem calls.
The D channel notifies the central office switch to send the incoming call to particular time slots on the
Cisco gateway or router. Each one of the B channels carries data or voice. The D channel carries
signaling for the B channels. The D channel identifies whether the call is a circuit-switched digital call
or an analog modem call. Analog modem calls are decoded and then sent off to the onboard modems.
Circuit-switched digital calls are directly relayed to the ISDN processor in the gateway.
When you configured ISDN PRI on the T1 or E1 controller, you automatically created a serial interface
that corresponds to the PRI group time slots. This interface is a logical entity that is associated with the
specific controller. After the serial interface is created, you must configure the D channel serial interface
that carries signaling. The configuration applies to all the PRI B channels (time slots) for that PRI group.
Figure 3
logical contents include 23 B channels, 1 D channel, 24 time slots, and 24 virtual serial interfaces (total
number of B + D channels).
Figure 3
Channel
type
B
B
B
B
•
•
•
•
•
B
B
B
D
When you configure your T1 controller for an NFAS backup D channel, a serial interface is
Note
automatically created only when your primary D channel fails.
Cisco AS5350XM and Cisco AS5400XM Universal Gateways Software Configuration Guide
22
shows the logical contents of an ISDN PRI interface used in a T1 network configuration. The
Logical Relationship of ISDN PRI Components for T1
Time slot
number
(data channel) 1
(data channel) 2
(data channel) 3
(data channel) 4
•
•
•
•
•
(data channel) 21
(data channel) 22
(data channel) 23
(signaling channel) 24
Basic Configuration Using the Command-Line Interface
Virtual
serial
interface
number
S0:0
S0:1
S0:2
S0:3
•
•
Logical
•
contents
•
of a PRI
•
interface
S0:20
S0:21
S0:22
S0:23