[c-nsp] Gigabit Interface Input Errors

[Ivan Gasparik]

Hi folks,

Does anybody know what causes the router to drop packets as
overrun and what as an input queue drops. There are two show interface
examples of NPE-G1, both with input hold-queue set to 4096. The first
one only shows 153 overrun packets, in the second interface output
you can see overruns together with input queue drops:

GigabitEthernet0/1 is up, line protocol is up 
...
  Input queue: 0/4096/0/58537 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/4096 (size/max)
  1 minute input rate 43040000 bits/sec, 6944 packets/sec
  1 minute output rate 23483000 bits/sec, 7180 packets/sec
     2609205324 packets input, 3131277093 bytes, 6 no buffer
     Received 2871721 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 2 throttles
     153 input errors, 0 CRC, 0 frame, 153 overrun, 0 ignored
     0 watchdog, 2871721 multicast, 0 pause input

GigabitEthernet0/3 is up, line protocol is up 
...
  Input queue: 0/4096/4258004/961350 (size/max/drops/flushes); Total output drops: 44638280
  Queueing strategy: Class-based queueing
  Output queue: 6/4096/0 (size/max total/drops)
  1 minute input rate 15685000 bits/sec, 5120 packets/sec
  1 minute output rate 28836000 bits/sec, 5171 packets/sec
     2503236491 packets input, 208082741 bytes, 589462 no buffer
     Received 1329388071 broadcasts (13 IP multicasts)
     0 runts, 12 giants, 960 throttles
     128042 input errors, 12 CRC, 0 frame, 128018 overrun, 0 ignored
     0 watchdog, 1424143105 multicast, 0 pause input

Thanks
Ivan


On Thursday 05 November 2009 21:38:53 Gert Doering wrote:
> Hi,
> 
> On Thu, Nov 05, 2009 at 01:41:16PM -0500, Drew Weaver wrote:
> > Does anyone have any tips on finding out what is causing it to
> > overrun?
> 
> "Hardware too slow error" - packets arrive in short bursts at line rate,
> and your router cannot handle that.
> 
> For example, an NPE-G1 will handle packets at, say, 300 mbit/sec if they
> come in evenly spaced - packet<pause>packet<pause>packet<pause> - but if
> 1000 packets arrive back-to-back and then a longer pause, it will
>  overrun the buffers.
> 
> 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".
> 
> We do some of both :-)
> 
> gert
>