[c-nsp] Arp Input Process Causing Spike in CPU

[Phil Mayers]

Rodney Dunn wrote:
> From 2500 to 5k?
> 
> How much time was between those captures?

Ha! Sorry for the confusion - that output is from 3 different routers 
(notice the hostnames in the prompts). I was trying to indicate that I 
have several boxes with large ARP tables.

> 
> I always recommend folks do "term exec prompt time" when
> getting outputs from Cisco boxes.
> 
> If you have that many arp entries it's pretty likely you may
> see some input queue drops if you don't bump the input queue depth
> up.
> 
> And check the arp socket queue in 'sh ip traffic':
> 
> ARP statistics:
>   Rcvd: 0 requests, 33 replies, 0 reverse, 0 other
>   Sent: 24 requests, 12 replies (0 proxy), 0 reverse
>   Drop due to input queue full: 0

That's useful to know, but not applicable here ;o)

Thanks for tip though. For general interest, one of the busier boxes 
reports:

ARP statistics:
   Rcvd: 136494153 requests, 4054789 replies, 749 reverse, 0 other
   Sent: 39674598 requests, 53305809 replies (52891590 proxy), 0 reverse
   Drop due to input queue full: 75

...for 17 weeks of uptime.

Cheers,
Phil