[c-nsp] recommendations for ARP CoPP

[Gert Doering]

Hi,

On Thu, Jan 05, 2006 at 02:04:30PM -0500, Matt Buford wrote:
> >How do "you other Sup720 users" out there handle ARP and CoPP?
> 
> I approach the problem from another angle, and enable broadcast storm 
> control on customer ports.  Each customer is individually limited, that way 
> one person flooding doesn't drop everyone else in the rate limit too.

Yes, this is a good suggestion.  (In our other datacenter, using 5500s,
we have broadcast storm control setup already - but that was years
ago, and I forgot all about it :) ).

OTOH, as far as I can see, broadcast storm control will at least
permit 1% of the port's bandwidth - so on a 100 Mbit port, I'll get
1 Mbit of (ARP) broadcasts, and on a GigE port, I'll get 10 Mbit...


Looking at it from yet another angle: what's the amount of ARP traffic
(or other "generic broadcasts") that a Sup720 could handle "quite 
comfortably", without interfering with other functions?  1 Mbit?  5 Mbit?

>From experience with other platforms, I'm *very* conservative regarding
packets directed at the box itself.


> I'm using almost exclusively 6500 switches, and the 6248 10/100 cards 
> support this, however the 6148 10/100/1000 cards do not.  :(

Fun stuff...

> Of course, not all ARPs are broadcast - but the looped ones you're seeing 
> likely are. 

Definitely.  The slave switch that they came in via (2948G) was completely
overwhelmed by the amount of broadcasts...

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de