
DO Commands and Administrative Tasks
Testing and troubleshooting
MAX Administration Guide
2-9
The DO Begin/End Rem LB command begins and ends a loopback at the serial host port at the
remote end of the call.
To begin a remote loopback, select DO Beg/End Rem LB. The call status character L appears
in the upper right-hand corner of the screen at both the local and the remote device. A remote
loopback tests the entire connection from host interface to host interface. The following events
occur:
1
The serial host interface of the local MAX unit begins the remote loopback test.
2
The data loops at the serial host interface of the remote MAX unit and comes back to the
local unit.
This loopback is also known as a remote data loopback, because the loopback occurs at the
DTE/DCE interface. To end a remote loopback, press Ctrl-D 6 (DO 6 on the palmtop
controller).
Unplugging the palmtop controller also terminates a remote loopback.
Keep in mind the following additional information:
•
A remote loopback disables data flow from the remote host, but the call remains online.
•
A remote loopback disables Dynamic Bandwidth Allocation (DBA).
•
Only switched and nailed-up channels active during the current call are looped back.
•
Drop-and-Insert channels are not looped back.
•
You must be in a port-specific edit menu or status window to use the DO Beg/End LB
command.
•
To allow the MAX unit time to complete handshaking, you must wait at least 20 seconds
between toggling the remote loopback on or off.
•
When the remote device is a not a Lucent Technologies inverse multiplexer, you cannot
set up a remote loopback if the network connection occurs over an ISDN line and the Call
profile includes any of the following settings:
–
Call Type is set to
1 Chnl
or
2 Chnl
.
–
Call Type is set to
AIM
or
BONDING
and Call Mgm is set to
Static
or
Mode 1
.
•
If the remote device is an ISDN Terminal Adapter (TA), the MAX unit cannot usually
perform a remote loopback. ISDN TAs cannot recognize the loopback signal. However,
most switching Channel Service Units/Data Service Units (CSU/DSUs) recognize the
remote loopback signal that the MAX unit sends, and remote loopbacks are usually
possible with such equipment.
•
The MAX unit uses a proprietary loopback message when the AIM management
subchannel is present (Call Mgm is set to
Manual
,
Dynamic
, or
Delta
in a Call
profile).
•
The MAX unit uses the CCITT V.54 loopback pattern when no management subchannel is
present (Call Type is set to
1 Chnl
or
2 Chnl
and
Call Mgm=Static
in a Call
profile).
•
If the MAX unit fails to set up a remote loopback, it establishes a loopback at the local
host interface that tried to establish the call.
•
The DO Beg/End LB command does not appear if you are not logged in with operational
privileges.