[74260] in North American Network Operators' Group
Re: L2 Broadcast/multicast limits on ethernet ports
daemon@ATHENA.MIT.EDU (Arien Vijn)
Mon Sep 20 14:49:10 2004
In-Reply-To: <20040920162507.66625.qmail@web88207.mail.re2.yahoo.com>
From: Arien Vijn <arien+nanog@ams-ix.net>
Date: Mon, 20 Sep 2004 20:46:58 +0200
To: nanog@merit.edu
Errors-To: owner-nanog-outgoing@merit.edu
On Sep 20, 2004, at 6:25 PM, KASHIF SALAMM wrote:
> We are looking into deploying the L2 broadcast/multicast limits on the=20=
> ethernet ports of=A0foundry switches.
Just to be sure, you mean that you want to add the following statements=20=
to your configuration?
broadcast limit x
multicast limit y
And there is also :
unknown-unicast limit x
> If anyone has case study or deployed it or any experience and don't=20
> mind sharing , will be very appreciated.
We applied limits on BigIron JetCore hardware. We had IronCore silicon=20=
before and applied on that hardware also.
All limits do work well. The switches start to drop the right types of=20=
frames as soon as the packet rates supersedes the respective limits.
But you need to be aware that these limits only apply to CPU forwarded=20=
frames. Hense it won't work as rate limiter on hardware (CAM) forwarded=20=
multicast frames. This also means that these features won't ease the=20
CPUs of switches receiving fast amounts of broadcast/multicast frames.=20=
But it can be used to limit broadcast storms propagating through your=20
L2-network.
Needless to say that, you must be careful if you use some kind of=20
layer-2 redundancy protocol. As most if not all use multicast frames.
Hope this helps, Arien
