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

[Sreejesh S]

Hi team 

My CISCO1941/K9 show some errors like interface is up but protocol down please check the below log and let me know the possibility of the particular issue

Router#sh interfaces serial 0/1/1
Serial0/1/1 is up, line protocol is down
  Hardware is WIC MBRD Serial
  Description: $van interface $
  Internet address is 117.239.xx.xx/30
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation HDLC, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:00, output 00:00:02, output hang never
  Last clearing of "show interface" counters 00:21:01
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/0 (size/max total/threshold/drops)
     Conversations  0/1/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 1158 kilobits/sec
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     263 packets input, 3682 bytes, 0 no buffer
     Received 263 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     126 packets output, 3024 bytes, 0 underruns
     0 output errors, 0 collisions, 42 interface resets
     263 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

[paul driver]

Hello

Check the clocking of the interfaces
One side should be running as DTC and the other as DCE ( this is usually your ISP CPE)
Check cabling also

Can you post:
show run int serial
show controllers | in Serial0/1/1

res

Paul

[Richard Burts]

On a serial interface like this line is up line protocol is down is an indication that keepalives have failed. There are several things that can cause this. Paul mentions clocking and that certainly can be a cause. I have seen this symptom when the device on the other end has been configured with "no keepalive" on its interface. I have also seen this symptom when the device on the other end of the connection was configured with a different serial protocol such as PPP or Frame Relay.

HTH

Rick

[me_noori]

if you cheched the above items then it is very  possible your wan interface is crashed

[MAHRISH]

Thank you Richard, I had the same problem, the clock rate and DCE/DTE was also good, the only thing that I had to touch was the encapsulation protocol which was misconfigured on one side of my Serial link.

[Richard Burts]

Thanks for letting us know. I am glad that my suggestion helped you find the solution for your problem.  This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.

HTH

Rick

[Nandy007]

Thanks so much it helped me lot.... I looked only for protocol mismatch and don't know about keep alive... after set up keep alive i am able to see line protocol up..

[Richard Burts]

I am glad that our suggestions were able to help you solve your problem. Thanks for letting us know. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.

[raku052000]

The same is happening with me. As I am connecting two serial interfaces that is of 7609 and 2900 router.  Encapsulation is ppp both side and i checked ip addresses too .I am using /30 network 

[Richard Burts]

You tell us that both sides are specifying PPP so mismatched protocol would not be the cause of your issue. You have not told us whether both sides are specifying keepalive, so that might be a possible cause if one does use keepalive and the other does not. But my guess at the most likely cause if that you have not configured clock rate on the DCE side of the connection.

Perhaps you can post the interface config from both routers and that might help us identify the issue.

HTH

Rick

[raku052000]

Thanks for the reply.  I even tried with the keepalive configuration..  Is there any timer to be configured,  because while debugging its pointing towards timer.  And can you give the 2900 serial interface mandatory configuration. 

Thanks and regards... 

Rakesh

[Meheretab Mengistu]

Hi Rakesh,

Could you share your configuration on the serial interfaces? We can look at it as well.

HTH,
Meheretab

[raku052000]

Hi guys..  Thanks for ur advices..  The issue resolved as the interface was faulty and we used another interface.