Hi James,

On 15/05/2013, at 12:29 AM, James S. Smith <jsm...@windmobile.ca> wrote:

> I'm looking for people's experience with storm control on Juniper switches.  
> We have a pair of EX4500 switches and I notice that storm control kicks in a 
> lot.  I'm concerned that it might be stopping legitimate broadcast and 
> multicast traffic.
> 

I would be concerned too - the fact that you're seeing this on a 4550 (assuming 
10G interfaces) - the defaults for storm control are pretty high (80% of link 
bandwidth for combined BUM traffic).  If you do a lot of multicast on your 
network, this may not be appropriate though, and there is a knob to 
specifically disable multicast from being counted:

set ethernet-switching-options storm-control interface all no-multicast

Without thinking too hard (it's late here), I would think with IGMP-Snooping 
turned on, there shouldn't be too many situations where a loop would cause 
multicast traffic to increase dramatically.

> So is storm control useful in a spanning tree environment, or is it 
> unnecessary?

I'm of the opinion that it is useful for the same reason that you enabled 
spanning-tree when you know there are no loops in your topology - it's there 
for that day when your intern gets their first simultaneous lesson in patching 
and broadcast domains.  

That said, I think though that you need to spend some time tuning it down for 
your environment.  Allowing up to 8Gbps of broadcast traffic isn't exactly 
"control".

Ben
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