[c-nsp] C6k 6708 Input drops

[Lee]

We weren't losing adjacencies, but were seeing lots of input queue
drops on a few 6704 ports configured as layer3 interfaces.  Bumping
the input queue size up to 4096 didn't make any difference, nor did
changing the input queue size on all vlan+L3 interfaces to 4096 (which
should have automatically adjusted spd thresholds) make any
difference.  But adding this got rid of almost all the drops:
  ip spd queue max-threshold 1000
  ip spd queue min-threshold 998

I don't remember getting an answer from Cisco about why the spd
thresholds weren't automatically adjusted on a 6500.  I tried changing
the input q size on all interfaces on a 7200 & spd thresholds were
automatically adjusted.  Dunno why it doesn't work on a 6500.

Lee


On 4/17/09, Antonio Soares <amsoares at netcabo.pt> wrote:
> I had the same type of problem weeks ago with 6704-10GE cards and i
> increased the input queue from the default to 2000 packets. But
> even with this change, i'm still getting input drops:
>
> +++++++++++++++++++++++
>   Input queue: 0/2000/259854/259783 (size/max/drops/flushes); Total output
> drops: 9766
>   Queueing strategy: fifo
>   Output queue: 0/40 (size/max)
>   30 second input rate 3422174000 bits/sec, 616164 packets/sec
>   30 second output rate 4781032000 bits/sec, 752303 packets/sec
>   L2 Switched: ucast: 3042490 pkt, 445190705 bytes - mcast: 701412 pkt,
> 55025811 bytes
>   L3 in Switched: ucast: 1443288206417 pkt, 1002589303485288 bytes - mcast:
> 0 pkt, 0 bytes mcast
>   L3 out Switched: ucast: 1777516490092 pkt, 1475677965625289 bytes mcast: 0
> pkt, 0 bytes
>      1443204358757 packets input, 1002494751199418 bytes, 0 no buffer
>      Received 755421 broadcasts (701411 IP multicasts)
>      0 runts, 0 giants, 0 throttles
>      18 input errors, 9 CRC, 9 frame, 0 overrun, 0 ignored
>      0 watchdog, 0 multicast, 0 pause input
>      0 input packets with dribble condition detected
>      1777485270815 packets output, 1475594581103091 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
> +++++++++++++++++++++++
>
> And sometimes the IGP adjacency goes down and i only can correlate with
> these input drops. I'm running 12.2(18)SXF15a.
>
> I have the impression that even using the maximum value allowed won't solve
> the issue.
>
> I'm now thinking about adjusting the SPD values in order to, at least, avoid
> the IGP issue.
>
> Comments are appreciated.
>
>
>
> Thanks.
>
> Antonio Soares, CCIE #18473 (R&S)
> amsoares at netcabo.pt
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Peter Rathlev
> Sent: sexta-feira, 17 de Abril de 2009 15:32
> To: Dhingra, Anand; Marian Ďurkovič
> Cc: cisco-nsp
> Subject: Re: [c-nsp] C6k 6708 Input drops
>
> On Fri, 2009-04-17 at 12:20 +0200, Marian Ďurkovič wrote:
>> Input drops on L3 interfaces include also drops seen by the RP.
>> These are not happening on the physical 10GE interface, but on the
>> CPU's input queue. Try looking for traffic directed to the switch
>> itself (SNMP, routing protocols etc) or traffic which is being punted
>> to CPU for some reason.
>
> On Fri, 2009-04-17 at 09:41 -0400, Dhingra, Anand wrote:
>> I am not sure why... but for some odd reason cisco only has a 75
>> packet buffer per interface going to the CPU.
>
> That was just the pieces of information I needed. I adjusted the hold-queue
> from 75 to 256 packets and the drops are now gone.
>
> Only thing left is to find out what those bursts are that the switch punts.
> But I'm very glad that there was an (easy to understand)
> explanation. :-)
>
> Thank you both of you!
>
> Regards,
> Peter
>
>
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