[c-nsp] 3750 High Cpu IP Input

[Ramcharan, Vijay A]

Last I checked "no ip unreachables" breaks PMTUD which can be fine in your environment or cause other serious problems. 
 
Vijay Ramcharan 
  
-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Lee
Sent: April 24, 2009 11:10
To: Marian Ďurkovič
Cc: Chris Lane; Richard Gallagher; cisco-nsp
Subject: Re: [c-nsp] 3750 High Cpu IP Input

On 4/24/09, Marian Ďurkovič <md at bts.sk> wrote:
> On Fri, Apr 24, 2009 at 10:01:08AM -0400, Lee wrote:
>> > These TTL=1 are causing the high CPU.
>
> Yes, those are not HW switched but punted to CPU in order to generate
> TTL_Exceeded ICMP message. Not sure if there's any knob to discard
> them silently.

I thought that's what "no ip unreachable" was for..


>> Just out of curiousity, would adding "ip multicast ttl-threshold 3"
>
> Beware, this is real evil. On most switch platforms this will completely
> disable HW forwarding of multicast packets and punt them *all* to CPU.

oops...  shows how much I know <grin>

Thanks,
Lee
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