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Looping a dsu 1wic 56k

Hello, I'm installing a 1841 for a customer and have a loop back plug inserted into the WIC. It's wired 1-4 and 2-5. The interface is up/down.

I thought by inserting ' service-module 56k clock source internal' it would force the interface into an up/up state? Interestingly enough the input/output buffers are incrementing and all of the control signals are up. any help would be appreciated.

Here's the state of the interface.

royalfreight#sh int s0/0/0
Serial0/0/0 is up, line protocol is down (looped)
  Hardware is GT96K with 56k 4-wire CSU/DSU
  Description: circuit id 64450178 network id 3852301138 
  Internet address is
  MTU 1500 bytes, BW 56 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP REQsent, loopback not set
  Keepalive set (10 sec)
  CRC checking enabled
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:00:38
  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, 1 packets/sec
  5 minute output rate 0 bits/sec, 1 packets/sec
     8 packets input, 112 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     8 packets output, 112 bytes, 0 underruns
     0 output errors, 0 collisions, 2 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     2 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

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Re: Looping a dsu 1wic 56k

Hello Michael,

the router has detected the loop:

>> Serial0/0/0 is up, line protocol is down (looped)

the protocol is down because the loop has been detected.

You can consider your test successful.

Hope to help


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