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Basic Configuration Using the Command-Line Interface on the Cisco VGD 1T3 Voice Gateway
Configuring the D Channels for ISDN Signaling
56
Cisco VGD 1T3 Voice Gateway Software Configuration Guide
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 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 1
shows the logical contents of an ISDN PRI interface used in a T1 network configuration. The
logical contents include 23 B channels, 1 D channel, 24 time slots, and 24 virtual serial interfaces (total
number of B + D channels).
Figure 1
Logical Relationship of ISDN PRI Components for T1
Note
When you configure your T1 controller for an NFAS backup D channel, a serial interface is
automatically created only when your primary D channel fails.
Command
Purpose
Step 1
Router>
enable
Enters privileged EXEC mode.
Step 2
Router#
configure terminal
Enters global configuration mode. You are in
global configuration mode when the prompt
changes to
Router(config)#.
B
(data channel)
1
S0:0
B
(data channel)
2
S0:1
B
(data channel)
3
S0:2
B
(data channel)
4
S0:3
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
B
(data channel)
21
S0:20
B
(data channel)
22
S0:21
B
(data channel)
23
S0:22
D
(signaling channel)
24
S0:23
35765
Channel
type
Time slot
number
Logical
contents
of a PRI
interface
Virtual
serial
interface
number
Содержание VGD-1T3
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Страница 120: ...Configuring Voice over IP Additional Resources 110 Cisco VGD 1T3 Voice Gateway Software Configuration Guide ...
Страница 196: ...Using the Setup Script Where to Go Next 186 Cisco VGD 1T3 Voice Gateway Software Configuration Guide ...