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Additional ISDN PRI configuration parameters include the following:
-
pri-group command
-
D-channel selection
-
Accepting analog calls
The
pri-group
Command
The
pri-group
command configures the specified
interface for PRI operation and the number of fixed timeslots that
are allocated on the provider's digital facility.
Router(config-controller)#pri-group
[timeslots range]
D-Channel Selection
The
interface serial
command specifies an interface for PRI D-channel operation. The interface is a serial interface to a T1/E1 on the router or access server:
Router(config)#interface serial { slot/port: |
unit:}{23 | 15}
Within 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, becomes serial subinterface 23.
Accepting Analog Calls
The
isdn incoming-voice modem
command allows incoming analog calls to be switched to internal modems that are installed on a digital network module. 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 available only for those access servers with the capability for internal modems:
Router(config-if)#isdn incoming-voice modem
Digital Modems for Analog Calls
Digital modem network modules do not provide network interfaces of their own; they handle analog calls passing through other router interfaces instead. In addition to the digital modem module, the router must contain a PRI network module to connect to the ISDN
channel, and must contain another module, such as Ethernet, to provide connectivity to the LAN. The PRI module concurrently handles digital ISDN data connections and remote voice-channel (analog) modem connections, allowing a dynamic mix of digital and modem connections. The digital modem module acts as a pool of available modems that can be used for both incoming and outgoing calls.
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