[c-nsp] 7600 RP Invalid Packet Drops

[Ivan]

I have a 7600 with a RSP720-3CXL-GE.  When pinging between the 7600 and 
any other device (I have tried a few) I am loosing packets - usually 
5/10000 ish.

I have eventually been able to match the number of lost packets with a 
counter from the output of "show ibc" which from my searching of the 
archives "shows you the inband interface leading to the RP CPU".  The 
counter is: Invalid pkts dropped: 306

Can anyone advise what this counter indicates?  Only seems to increment 
with my ping traffic and not any customer traffic.  I have other similar 
hardware but can not reproduce the issue :-(

The output

7600#show ibc
Interface information:
         Interface IBC0/0(idb 0x1C88ECE8)
         5 minute rx rate 1138000 bits/sec, 156 packets/sec
         5 minute tx rate 2305000 bits/sec, 306 packets/sec
         1529092452 packets input, 97618397184 bytes
         1480180863 broadcasts received
         1522436849 packets output, 93778000882 bytes
         15858294 broadcasts sent
         0 Bridge Packet loopback drops
         1415112685 Packets CEF Switched, 0 Packets Fast Switched
         0 Packets SLB Switched, 0 Packets CWAN Switched
         Label switched pkts dropped: 0    Pkts dropped during dma: 0
         Invalid pkts dropped: 306    Pkts dropped(not cwan consumed): 0
         Xconnect pkts processed: 29, dropped: 0
         Xconnect pkt reflection drops: 0
         Total paks copied for process level 29
         Total short paks sent in route cache 1346148563
         Total throttle drops 0    Input queue drops 0
         total spd packets classified (50929199 low, 6698050 medium, 
34521686 high)
         total spd packets dropped (0 low, 0 medium, 0 high)
         spd prio pkts allowed in due to selective throttling (0 med, 0 
high)
         IBC resets   = 1; last at xxx 2010

Driver Level Counters: (Cumulative, Zeroed only at Reset)
           Frames          Bytes
   Rx(0)   878738849       2018480538
   Rx(1)   653772091       3242895654
   Tx(0)   1522436850      1746755712

  Input Drop Frame Count
      Rx0 = 0                Rx1 = 0
  Per Queue Receive Errors:
      FRME   OFLW   BUFE   NOENP  DISCRD DISABLE BADCOUNT
  Rx0 0      0      0      0      0        0    0
  Rx1 0      0      0      0      0        0    0


   Tx Errors/State:
    One Collision Error   = 0            More Collisions       = 0
    No Encap Error        = 0            Deferred Error        = 0
    Loss Carrier Error    = 0            Late Collision Error  = 0
    Excessive Collisions  = 0            Buffer Error          = 0
    Tx Freeze Count       = 0            Tx Intrpt Serv timeout= 1

   Counters collected at Idb:
    Is input throttled    = 0            Throttle Count        = 0
    Rx Resource Errors    = 0            Input Drops           = 306
    Input Errors           = 0
    Output Drops          = 0            Giants/Runts          = 0/0
    Dma Mem Error         = 0            Input Overrun         = 0

7600#show platform hardware pfc mode
PFC operating mode : PFC3CXL

Cheers

Ivan