[c-nsp] Serial link CTS=down link UP

[Michael K. Smith - Adhost]

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Marcelo Zilio
> Sent: Thursday, December 17, 2009 10:04 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Serial link CTS=down link UP
> 
> Hi,
> 
> Has anyone seen this in serial interfaces before?
> Link is UP and traffic is going through, however router shows CTS=down
> besides a lot CRCs/Input Errors.
> It doesn't make sense to me the parameter which should advise that the
> link
> is "ready to go" is DOWN while there is traffic on it.
> Users are complaining some application are slow.
> 
> The router is a Cisco 2811 IOS 12.4(15)T10.
> 
> Router#sh int s0/1/0
> Serial0/1/0 is up, line protocol is up
>   Hardware is GT96K Serial
>   MTU 1500 bytes, BW 256 Kbit/sec, DLY 20000 usec,
>      reliability 255/255, txload 40/255, rxload 42/255
>   Encapsulation FRAME-RELAY IETF, loopback not set
>   Keepalive set (10 sec)
>   CRC checking enabled
>   LMI enq sent  48, LMI stat recvd 48, LMI upd recvd 0, DTE LMI up
>   LMI enq recvd 0, LMI stat sent  0, LMI upd sent  0
>   LMI DLCI 0  LMI type is ANSI Annex D  frame relay DTE  segmentation
> inactive
>   FR SVC disabled, LAPF state down
>   Broadcast queue 0/64, broadcasts sent/dropped 7/0, interface
> broadcasts 0
>   Last input 00:00:00, output 00:00:00, output hang never
>   Last clearing of "show interface" counters 00:07:55
>   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
0
>   Queueing strategy: dual fifo
>   Output queue: high size/max/dropped 0/256/0
>   Output queue: 0/128 (size/max)
>   30 second input rate 43000 bits/sec, 68 packets/sec
>   30 second output rate 41000 bits/sec, 78 packets/sec
>      34746 packets input, 2956769 bytes, 0 no buffer
>      Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
>      602 input errors, 602 CRC, 433 frame, 107 overrun, 0 ignored, 323
> abort
>      43237 packets output, 3308125 bytes, 0 underruns
>      0 output errors, 0 collisions, 0 interface resets
>      0 unknown protocol drops
>      0 output buffer failures, 0 output buffers swapped out
>      0 carrier transitions
>      DCD=up  DSR=up  DTR=up  RTS=up  *CTS=down*
> 
With all those errors I would say you have a physical layer problem or a
clocking issue.  Perhaps the CTS is flapping between up and down and
you're catching it on the down.  What happens if you debug the
interface?

Regards,

Mike