[c-nsp] Gigabit Interface Input Errors

[NMaio at guesswho.com]

Ryan,
I have similar problems with 4500s so I keep a close eye on the detailed counters.  In particular I watch the transmit drops and also the receive buffer stats.  Pauses frames also indicate a problem in our environment and I would expect in some other environments.  It's a long output but I have always found it very helpful since the reason for the input/output errors are not always evident in a show interface output.
 

show int counters detail

Port       Tx-Drops-Queue-1  Tx-Drops-Queue-2 Tx-Drops-Queue-3  Tx-Drops-Queue-4
Gi5/34                    0                 0                0                 0
Gi5/35                    0                 0                0                 0
Gi5/36                    0                 0                0                 0
Gi5/37                    0                 0                0                 0
Gi5/38                    0                 0                0                 0
Gi5/39                    0                 0                0                 0
Gi5/40                    0                 0                0                 0
Gi5/41                    0                 0                0                 0
Gi5/42                    0                 0                0                 0
Gi5/43                    0                 0                0                 0
Gi5/44                    0                 0                0                 0
Gi5/45                    0                 0                0                 0
Gi5/46                    0                 0                0                 0
Gi5/47                    0                 0                0                 0
Gi5/48                    0                 0                0                 0
Gi7/1           21257797383                 0                0                 0

show int counters detail
..
...
Port         Rx-No-Pkt-Buff     RxPauseFrames    TxPauseFrames   PauseFramesDrop
Gi4/26                    0                 0                0                 0
Gi4/27                    0                 0                0                 0
Gi4/28                    0                 0                0                 0
Gi4/29                    0                 0                0                 0
Gi4/30                    0                 0                0                 0
Gi4/31                    0                 0                0                 0
Gi4/32                    0            107830                0                 0
Gi4/33                    0                 0           346468                 0
Gi4/34                    0                 0                0                 0
Gi4/35                    0                 0                0                 0
Gi4/36                    0                 0                0                 0
Gi4/37                    0                 0             9056                 0
Gi4/38                    0                 0                0                 0
Gi4/39                    0                 0                0                 0
Gi4/40                    0                 0           240746                 0
Gi4/41                 1548                 0                0                 0
Gi4/42                    0                 0          1390048                 0

Nick



-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Ryan West
Sent: Thursday, November 05, 2009 4:11 PM
To: Gert Doering; Drew Weaver
Cc: 'cisco-nsp at puck.nether.net'
Subject: Re: [c-nsp] Gigabit Interface Input Errors

Hi,

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Gert Doering
> Sent: Thursday, November 05, 2009 3:39 PM
.
> 
> There's not much you can do, except "get a hardware forwarding box"
> or "just accept it, and only worry if the errors increase more
> frequently".

Hopefully I'm not completing high-jacking here, but I have seen similar issues on the 4500 w/WS-X4548-GB-RJ45 line cards.  The fabric has 6gbps per slot, so the oversubscription is 8:1.  The best tell tale sign that I'm hitting oversubscription are input errors with no CRC or overruns, like below:

  30 second input rate 6394000 bits/sec, 719 packets/sec
  30 second output rate 722000 bits/sec, 481 packets/sec
     770898484 packets input, 957181248327 bytes, 0 no buffer
     Received 594832 broadcasts (560167 multicast)
     0 runts, 0 giants, 0 throttles
     282191 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 input packets with dribble condition detected
     455543646 packets output, 153140605424 bytes, 0 underruns 

Is there a more systematic approach to detecting this?  I've gone through some docs and most useful information is geared toward the 6500, such as http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801751d7.shtml#ASIC.  Currently I have to use a combination of interface statistics and historical Cacti graphs to narrow down over-utilized port ranges.

Thanks,

-ryan
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