[c-nsp] Dropped packets

[Fredrik.Jacobsson at enskilda.se]

Hi!

Hoping that someone can point me in the right direction...
I have two 2811 at a site. Each has one T1-interface (WIC-1T) for leased
line
wan-connection to HQ. (they also have a two-port T1 MFT-card each for phone
services)

Lately I've gotten output drops on both routers, even when we dont have
enough traffic to fill the buffers.
Perhaps like 10% bandwith usage, and still drops.

>sho int ser 0/0/0
Serial0/0/0 is up, line protocol is up 
  Hardware is GT96K Serial
  Description: Blablabla
  Internet address is x.x.x.x/30
  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, 
     reliability 255/255, txload 14/255, rxload 1/255
  Encapsulation PPP, LCP Open
  Open: IPCP, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:28, output 00:00:00, output hang never
  Last clearing of "show interface" counters 2d03h
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 607494
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/607494 (size/max total/threshold/drops) 
     Conversations  0/18/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 1158 kilobits/sec
  5 minute input rate 0 bits/sec, 63 packets/sec
  5 minute output rate 881000 bits/sec, 91 packets/sec
     11730227 packets input, 91596 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 1 giants, 0 throttles
     3 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored, 3 abort
     8842506 packets output, 3950408912 bytes, 0 underruns
     0 output errors, 0 collisions, 3 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

Any suggestions for further troubleshooting is highly appreciated.

Interface configuration looks like this:
interface Serial0/0/0
 description Blablabla
 bandwidth 1544
 ip address x.x.x.x 255.255.255.252
 encapsulation ppp
 no cdp enable

I'm thinking the drops may have been introduces with the command:
network-clock-select 1 T1 0/1/0
So I'm going to revert back to the old setting tonight.
But then we get slip-errors on the MFT-interfaces, so it's not the way to go
for a permanent solution.

What, other than full usage of the available bandwith, may cause drops?
Any suggestions? cpu-usage is ok. we're (of course) using cef.
Were encrypting all wan-traffic. Would problems there be indicated by the
output drops counter on the interface? I think not.

We're currently using 12.3(11)T3

Thanks
/Fredrik Jacobsson





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