[c-nsp] Catalyst LAN Input Errors Query...

[Peter Rathlev]

On Thu, 2008-11-06 at 14:24 -0500, Howard Leadmon wrote:
> FastEthernet9/48 is up, line protocol is up (connected)
>   Hardware is C6k 100Mb 802.3, address is 0004.de66.8f73 (bia
>                                                     0004.de66.8f73)
>     MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, 
>      reliability 255/255, txload 3/255, rxload 24/255
>   Encapsulation ARPA, loopback not set
>   Keepalive set (10 sec)
>   Full-duplex, 100Mb/s
>   input flow-control is off, output flow-control is unsupported 
>   ARP type: ARPA, ARP Timeout 04:00:00
>   Last input never, output 00:00:43, output hang never
>   Last clearing of "show interface" counters 00:12:47
>   Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output
>                                                            drops: 0
>   Queueing strategy: fifo
>   Output queue: 0/40 (size/max)
>   1 minute input rate 9759000 bits/sec, 1396 packets/sec
>   1 minute output rate 1505000 bits/sec, 1110 packets/sec
>      1067610 packets input, 920823086 bytes, 0 no buffer
>      Received 0 broadcasts (0 multicasts)
>      0 runts, 0 giants, 0 throttles 
>      980 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
>      0 watchdog, 0 multicast, 0 pause input
>      0 input packets with dribble condition detected
>      839374 packets output, 146203703 bytes, 0 underruns
>      0 output errors, 0 collisions, 0 interface resets
>      0 babbles, 0 late collision, 0 deferred
>      0 lost carrier, 0 no carrier, 0 PAUSE output
>      0 output buffer failures, 0 output buffers swapped out
> 
> Notice that in less than 15 min I have almost 1000 input errors, but
> the other more detailed counters show nothing.  I have had the cable
> swapped, and the LAN card in the PC swapped, still the same results.

Well, a thousand errors may sound like much, but it's less than 0.1% of
the total number of packets received.

> What is just an input error?   Is this bad hardware, something I should
> just expect on some interfaces to PC's, or what?  
> 
> I have googled around a bit, looked on Cisco's site, and everything
> says that the input error counter is just the combined count of the
> other counters like CRC, overrun, and so on, but they are all 0 for
> me..
> 
> Any clues on where to look or what would cause this???

What type of card is it? If you have an oversubscribed path to the
backplane the switch might drops packets there. AFAIK there's no
surefire way to find out though.

Input flow control might help reducing lost packets if they're caused by
oversubscription / too small buffers. This assumes the server NICs know
flow-control of course.

Do you have any interface on a similar module with similar traffic/load
patterns that is not experiencing these errors?

Regards,
Peter