Soft loop test a T1

JTx · ‎10-18-2017

Hello,

I performed the following steps:

Router#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#controller t1 0
Router(config-controller)#no pri-group timeslots 1-24
Router(config-controller)#channel-group 0 timeslots 1-24 speed 64

!--- This automatically creates a single Serial0:0 interface. 

Router(config-controller)#loopback local line

!--- The loopback local command above is only necessary for software loopbacks.

Router(config-controller)#exit
Router(config)#interface serial 0:0 
Router(config-if)#encapsulation hdlc

!--- Note: All loopback testing is done with hdlc encapsulation.

However, the interface shows UP/DOWN and I cannot (locally) generate ping packets to the IP address configured on this interface.

Serial0/0/1:0 is up, line protocol is down
Hardware is DSX1

!

T1 0/0/1 is up. (Local Line Loopback)
Applique type is Channelized T1
Cablelength is long 0db
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 FPGA Rev: 08121917, FPGA Type: PRK4
Framing is ESF, FDL is ansi & att, Line Code is B8ZS, Clock Source is Line.
CRC Threshold is 320. Reported from firmware is 320.

I want to perform a soft loop test to rule out any potential issues with the T1 card/port. I plan to send ping packets to the IP addresss configured on that port.

I have noticed that sending packets size equal or larger to 300 bytes causes a packet drop pattern, the ISP says that the issue might be on our end.

Thanks in advance.

Flavio Miranda · ‎10-18-2017

Hello @JTx

Usually Serial0/0/1:0 is up, line protocol is down means different encapsulation on both both side. You are using HDLC, confirm which Encapsulation ISP is currently using.

-If I helped you somehow, please, rate it as useful.-

JTx · ‎10-18-2017

Thanks Flavio,

I checked with the ISP, they are using PPP. But even if I set the serial interface to PPP the interface remains UP/DOWN when the "loop local" command is applied under Controller T1 0/0/1.

Flavio Miranda · ‎10-18-2017

If they are using PPP you need to use it as well. They need to speak the same language.

Can you share the show run from this device?

JTx · ‎10-23-2017

Flavio Thank you so much. Changing the encapsulation to HDLC actually worked!

I do have another question, though. I tested the Serial interface with the loop in place from the provider and I got a weird pattern:

RTR#ping 172.16.255.129 rep 1000 size 1500
Type escape sequence to abort.
Sending 1000, 1500-byte ICMP Echos to 172.16.255.129, timeout is 2 seconds:
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.!!!!!!!!!.
!!!!!!!!!.!!!!!!!!!.
Success rate is 90 percent (900/1000), round-trip min/avg/max = 20/22/100 ms

Serial0/0/1:0 is up, line protocol is up (looped)
Hardware is DSX1
Internet address is 172.16.255.129/30
MTU 1500 bytes, BW 1536 Kbit/sec, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, crc 16, loopback not set
Keepalive set (10 sec)
Last input 00:00:08, output 00:00:08, output hang never
Last clearing of "show interface" counters 00:25:07
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
3958 packets input, 5723962 bytes, 0 no buffer
Received 156 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
3958 packets output, 5723962 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions

T1 0/0/1 is up.
Applique type is Channelized T1
Cablelength is long 0db
No alarms detected.
alarm-trigger is not set
Soaking time: 3, Clearance time: 10
AIS State:Clear LOS State:Clear LOF State:Clear
Version info FPGA Rev: 08121917, FPGA Type: PRK4
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 (258 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
Data in Interval 1:
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

Any idea what might be causing this? Thanks in advance