Cisco 1841 Serial interface issue

Unanswered Question
Mar 13th, 2012
User Badges:


i have one problem in my client end router(cisco 1841).

In that they have leased line with 128 kbps.

But the link is down.

I take the router through console for troubleshooting.

while i check with the serial interface they show output like this.

Serial0/1/0 is down, line protocol is down

  Hardware is GT96K Serial

  Internet address is

  MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation PPP, LCP Closed, loopback not set

  Keepalive set (10 sec)

  CRC checking enabled

  Last input never, output 00:07:21, output hang never

  Last clearing of "show interface" counters 00:16:13

  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

     0 packets input, 0 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

     27 packets output, 378 bytes, 0 underruns

     0 output errors, 0 collisions, 2 interface resets

     0 output buffer failures, 0 output buffers swapped out

     12 carrier transitions

     DCD=down  DSR=up  DTR=up  RTS=up  CTS=up

If DCD down means how to troubleshoot?

what is DCD??

can anyone tell me where is the issue.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Dan-Ciprian Cicioiu Tue, 03/13/2012 - 02:40
User Badges:
  • Gold, 750 points or more

Hi ,

DCD means carrier detect , so in your case there is no carrier.

The issue is the link. If the link is offered by a provider I would ask them to check the circuit.


kumarpmt83 Tue, 03/13/2012 - 02:44
User Badges:

if it is chance have any problem in serial cable or modem.

Dan-Ciprian Cicioiu Tue, 03/13/2012 - 03:28
User Badges:
  • Gold, 750 points or more


I do belive that the circuit is the problem. As far as I know:

    DSR is the terminal ready , in you case up , the router receives the modem ready , so the serial cable is not the problem

    DCD down means that the local modem cannot communicate with the other end modem.



kumarpmt83 Tue, 03/13/2012 - 04:54
User Badges:

Thanks for ur Information.

In case any modem or serial cable problem means which of the parameter to be down.

How to find that.

Dan-Ciprian Cicioiu Tue, 03/13/2012 - 05:13
User Badges:
  • Gold, 750 points or more

Hi ,

DCD, CTS , DSR - are provided by the dce in your case the modem

DTR , RTS - are provided by the dte in your case the router.

If CTS and DSR are down and DTR and RTS are up ,this can be a modem or a cable problem.




This Discussion