Information Technology Reference
In-Depth Information
Run the
show controller t1
exec command after each step to see whether the controller exhibits any
errors.
If the Line Is in Loopback Mode
Check to see whether the line is in loopback mode from the
show controller t1
output. A line should be
in loopback mode only for testing purposes.
To turn off loopback, use the
no loopback
command in the controller configuration mode, as shown
here:
maui-nas-03(config-controlle)#
no loopback
If the Controller Displays Any Alarms
Check the
show controller
command output to see if there are alarms displayed by the controller.
We will now discuss various alarms and the procedure necessary to correct them.
Receive (RX) Alarm Indication Signal (AIS) (Blue)
A received alarm indication signal (AIS) means that an alarm is occurring on the line upstream of the
equipment connected to the port. The AIS failure is declared when an AIS defect is detected at the input
and still exists after the loss of frame failure is declared (caused by the unframed nature of the “all-ones”
signal). The AIS failure is cleared when the loss of frame failure is cleared.
Check to see whether the framing format configured on the port matches the framing format of the line.
If not, change the framing format on the controller to match that of the line.
Step 1
Contact your service provider to check for misconfiguration within the telco.
Step 2
Receive (Rx) Remote Alarm Indication (Yellow)
A received remote alarm indication means that the far-end equipment has a problem with the signal that
it is receiving from its upstream equipment.
For SF links, the far-end alarm failure is declared when bit 6 of all the channels has been zero for at least
335 ms. The failure is cleared when bit 6 of at least one channel is not zero for a period usually less than
1 second and always less than 5 seconds. The far-end alarm failure is not declared for SF links when a
loss of signal is detected.
For ESF links, the far-end alarm failure is declared if the yellow alarm signal pattern occurs in at least
seven out of ten contiguous 16-bit pattern intervals. The failure is cleared if the yellow alarm signal
pattern does not occur in ten contiguous 16-bit signal pattern intervals.
Step 1
Insert an external loopback cable into the port. To create a loopback plug, refer to the section
“Performing Hardware Loopback Plug Test,” later in this chapter.
Step 2
Check to see if there are any alarms. If you do not see any alarms, then the local hardware is probably
in good condition. In that case, do the following:
•
Check the cabling. Refer to the section “If Receiver Has Loss of Signal” for more information.
