Forwarding issues related to MACs starting with a 4 or a 6 (Was: [c-nsp] Wierd MPLS/VPLS issue)

Christopher Morrow morrowc.lists at
Fri Dec 2 16:07:43 UTC 2016

On Fri, Dec 2, 2016 at 11:02 AM, Simon Lockhart <simon at> wrote:

> On Fri Dec 02, 2016 at 10:29:56AM -0500, Christopher Morrow wrote:
> > you'd think standard testing of traffic through the asic path somewhere
> > between 'let's design an asic!' and 'here's your board ms customer!'
> would
> > have found this sort of thing, no? or does testing only use 1 mac address
> > ever?
> Well, it's actually payload, rather than src/dst MAC used for forwarding,
> so
> there's quite a few more combinations to look for...
> 2^(8*9216) is quite a lot of different packets to test through the
> forwarding
> path... But, wait, that assumes every bit combination for 9216 byte
> packets,
> but the packet might be shorter than that... So multiply that by (9216-64).
but  most/all forwarding asics (aside from perhaps extreme's?) only deal
with the first N bits in the header (128 or so..) so... not quite as many

> Anyone want to work out how many years that'd take to test, even at 100G?
> Simon

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