Specifications

Configure Serial Interfaces for CSU/DSU Service Modules

IC-110

Cisco IOS Interface Configuration Guide

In switched mode, you need additional dialer conﬁguration commands to conﬁgure dial-out

numbers. Before you enable the service-module 56k network-type switched command, both

CSU/DSU’s must use a clock source coming from the line and the clock rate conﬁgured to auto or

56k kbps. If the clock rate is not set correctly, this command will not be accepted.

The 2-wire and 4-wire, 56/64-kbps CSU/DSU modules use V.25 bis dial commands to interface with

the router. Therefore, the interface must be conﬁgured using the dialer in-band command. DTR dial

is not supported.

Note Any loopbacks in progress are terminated when switching between modes.

Enable Acceptance of a Remote Loopback Request

To enable the acceptance of a remote loopback request on a 2- or 4-wire, 56/64-kbps CSU/DSU

module, use the following command for a serial interface in interface conﬁguration mode:

The no service-module 56k remote-loopback command prevents the local CSU/DSU from being

placed into loopback by remote devices on the line. Unlike the T1 module, the 2- or 4-wire,

56/64-kbps CSU/DSU module can still initiate remote loopbacks with the no form of this command

conﬁgured.

Select a Service Provider

To select a service provider to use with a 2- or 4-wire, 56/64 kbps dial-up line, use the following

command for a serial interface in interface conﬁguration mode:

The att keyword speciﬁes AT&T or another digital network service provider as the line carrier,

which is the default for the 4-wire, 56/64-kbps CSU/DSU module. The sprint keyword speciﬁes

Sprint or another service provider whose network carries mixed voice and data as the line carrier,

which is the default for the 2-wire switched 56-kbps CSU/DSU module.

In a Sprint network, echo-canceler tones are sent during call setup to prevent echo cancelers from

damaging digital data. The transmission of these cancelers may increase call setup times by

8 seconds on the 4-wire module. Having echo cancellation enabled does not affect data trafﬁc.

This conﬁguration command is ignored if the network type is DDS.

Use the no form of this command to enable the default service provider. AT&T is enabled by default

on the 4-wire, 56/64 module. Sprint is enabled by default on the 2-wire switched 56 module.

Command Purpose

service-module 56k remote-loopback Enable a remote loopback request.

Command Purpose

service-module 56k switched-carrier {att |

other | sprint}

Select a service provider for a 2 or 4 wire switched

56/64 kbps dialup line.