Hi,

Yes ICMP is handled by the CPU of the PFE. We can check ICMP throttled at this 
level.  
As you said, a firewall filter at the interface level works. Thank you

Regards,
David



 
David Roy
Orange France - RBCI IP Technical Assistance Center
Tel.   +33(0)299876472
Mob. +33(0)685522213
Email. david....@orange-ftgroup.com
 

-----Message d'origine-----
De : Richard A Steenbergen [mailto:r...@e-gerbil.net] 
Envoyé : vendredi 30 avril 2010 00:23
À : ROY David DTF/DERX
Cc : juniper-nsp@puck.nether.net
Objet : Re: [j-nsp] Disable ICMP Time Exceeded

On Thu, Apr 29, 2010 at 05:04:20PM +0200, david....@orange-ftgroup.com wrote:
> Hi all,
> 
> Is-there a way to disable or rate-limit (in junos) the sending of ICMP 
> Time Exceeded when the box receives datagrams with a TTL expired.

Not directly afaik. You could firewall packets that are about to TTL expire, so 
they never get processed in the first place. The ICMP generation is handled by 
the PFE CPU, so I'm not sure if a lo0 filter would affect that, but a physical 
interface filter should work.

Usually the issue is the opposite from the hard coded ICMP generation rate 
limit which you can't tweak, i.e. as soon as some customer points a default 
route back at you and creates a small routing loop your router starts looking 
shitty in traceroute and even idiot on the Internet with mtr and/or visual 
traceroute descends upon your noc email/phone like a swarm of locusts. You 
haven't lived until you've received a complaint in the form of a windows 
desktop screenshot of a tracert.exe window embedded in a word document, zipped, 
with porn windows open in the background.

-- 
Richard A Steenbergen <r...@e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)

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