Showing results for 
Search instead for 
Did you mean: 

Serial interface troubleshooting - Line Loop

Pradeep H A
Level 1
Level 1
I am looking for some explanation regarding the below output from one of our Cisco routers. Its a CE Router.
> Where exactly is the loop placed?
> Loop is facing which direction?
> What does that inband CSU code mean?
> If I bounce this controller will loop be gone? why?
T1 0/2/0 is up.          (Line Looped (inband CSU code)) (Line Loop by Remote)
Applique type          is Channelized T1
Cablelength is short 110
Receiver has no          alarms.
alarm-trigger is not set
Soaking time: 3, Clearance          time: 10
AIS State:Clear LOS State:Clear LOF State:Clear
Version          info Firmware: 20090408, FPGA: 13, spm_count = 0
Framing is ESF,          FDL is ansi & att, Line Code is B8ZS, Clock Source is Line.
CRC          Threshold is 320. Reported from firmware is 320.
Data in current          interval (370 seconds elapsed):
0 Line Code Violations, 0 Path Code          Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded          Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0          Unavail Secs
Total Data (last 24 hours)
62 Line Code Violations,          11411 Path Code Violations,
48 Slip Secs, 7 Fr Loss Secs, 11 Line          Err Secs, 18 Degraded Mins,
195 Errored Secs, 145 Bursty Err Secs,          7 Severely Err Secs, 13055 Unavail Secs
Thanks a lot in advance
1 Accepted Solution

Accepted Solutions

That is correct. However as mentioned above, you real issue is apparently, a faulty circuit.

View solution in original post

3 Replies 3

paolo bevilacqua
Hall of Fame
Hall of Fame

Considering the high number of errors, the loop may have random happened.

You can read and search online for information about remote loop, etc.

Get the circuit fixed, that is the important thing and the one you should worry instead.


Someone told me that a remote device has sent an "Inband CSU code" in response to which the CE router has put a loop on its own controller facing the network/PE/Service provider. Was expecting if someone with expertise could confirm it.

             Secondly Can someone confirm if the loop could be cleared with a shut - no shut on the controller?


That is correct. However as mentioned above, you real issue is apparently, a faulty circuit.

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Review Cisco Networking products for a $25 gift card