Hardware manual

loopback remote (interface)

Interface Commands IR-147

Syntax Description for 2- and 4-Wire, 56/64-kbps CSU/DSU Modules

Default

Disabled

Command Mode

Interface conﬁguration

Usage Guidelines

This command ﬁrst appeared in Cisco IOS Release 11.0.

This command applies only when the remote CSU/DSU device is conﬁgured for this function. It is

used for testing the data communication channels along with or without remote CSU/DSU circuitry.

The loopback is usually performed at the line port, rather than the DTE port, of the remote

CSU/DSU.

For a multiport interface processor connected to a network via a channelized T1 link, the loopback

remote interface conﬁguration command applies if the remote interface is served by a DDS line (56

kbps or 64 kbps) and the device at the remote end is a CSU/DSU. In addition, the CSU/DSU at the

remote end must react to latched DDS CSU loopback codes. Destinations that are served by other

types of lines or that have CSU/DSUs that do not react to latched DDS CSU codes cannot participate

in an interface remote loopback. Latched DDS CSU loopback code requirements are described in

AT&T speciﬁcation TR-TSY-000476, “OTGR Network Maintenance Access and Testing.”

For the integrated FT1/T1 CSU/DSU module, the loopback remote full command sends the loopup

code to the remote CSU/DSU. The remote CSU/DSU performs a full-bandwidth loopback through

the CSU portion of the module. The loopback remote payload command sends the loopup code on

the conﬁgured timeslots, while maintaining the D4-extended super framing. The remote CSU/DSU

performs the equivalent of a loopback line payload request. The remote CSU/DSU loops back only

those timeslots that are conﬁgured of the remote end. This loopback reframes the data link,

regenerates the signal, and corrects bi polar violations and extended super frame CRC errors. The

loopback remote smart-jack command sends a loopup code to the remote smart jack. You cannot

put the local smart jack into loopback.

Failure to loopup or initiate a remote loopback request could be caused by enabling the

no service-module t1 remote-loopback command or having an alternate remote-loopback code

conﬁgured on the remote end. When the loopback is terminated, the result of the pattern test is

displayed.

2047 Transmits a pseudo-random test pattern that repeats after 2047 bits.

511 Transmits a pseudo-random test pattern that repeats after 511 bits.

stress-pattern

pattern number

Transmits a DDS stress pattern available only on the 4-wire 56/64-kbps

CSU/DSU module. You may enter a stress pattern from 1 to 4. A 1 pattern

sends 100 bytes of all 1s and then 100 bytes of all 0s to test the stress

clocking of the network. A 2 pattern sends 100 bytes of a 0x7e pattern then

100 bytes of all 0s. A 3 pattern sends continuous bytes of a 0x46 pattern. A 4

pattern sends continuous bytes of 0x02 pattern.