On 2022-08-06 06:15, Saku Ytti via cisco-nsp wrote:
On Sat, 6 Aug 2022 at 05:27, Paul via cisco-nsp
<cisco-nsp@puck.nether.net> wrote:
Storm control pps is bugged on the 10g ports on the older 4900
platforms, 4948E , 4900M, sup6 platforms.
My guess would be that PPS is not supported by the hardware and
behaviour is undefined, and you would need to poke hardware to
understand what was actually programmed when you asked it to PPS, i.e.
it hasn't worked as desired in the 1GE either.
An aside, but an example of where this can go wrong...
I once came a-cropper of an Extreme X440 doing something interesting
with its configured broadcast/multicast limits; if you configured
'5000pps' as the storm-control limit, it would be divided by 1000 &
measured every millisecond, so in fact the "real limit" was 5 frames per
millisecond. This undocumented (at the time?) behaviour meant that any
ports with multiple VLANs - especially those carrying FHRP - would
immediately shutdown, because more than 5 multicast frames would be
received more or less together.
The alternative is, of course, to have a counter that can be read/reset
every second - but what if your ASIC can't do that?
Given the era of hardware, I do wonder if simply multiplying the
configured storm-control limit by 10 will be sufficient to elect the
exact same behaviour on the TE port. I'd hazard a guess that some bit of
code is dividing by ten, and that's why it can't do 'per second'
storm-control. I loved my 4900Ms muchly (gert is a big meanie) but I
must confess I don't think I ever had (nor wanted) a customer-facing L2
TenGig port.
Tom
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