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Re: IPv6 Link-Local Use Issue for Applications



Hi Bob, Alan,

My reply to Bob's question at end.

On Tue, 19 Aug 2003 19:48:26 -0400 (EDT)
"Alan E. Beard" <aeb1@aebeard.com> wrote:

> Bob:
> 
<snip>
> 
> This is not an urban legend, but, based on my experience, manufacturers
> tend to react vigorously and very rapidly indeed to remove from public
> circulation _all_ cards bearing MAC addresses which may have been
> duplicated.
> 

The story I'd heard was the problem most often occured at the bottom end of the NIC market, rather than the top ie. the el-cheapo cards manufactured in Taiwan etc.

The two reasons were 

1) The NIC manufacturer couldn't be bothered with getting an official OUI from IEEE, due to the costs involved cutting into their profit margin (although I'd assumed it cost money to get an OUI, if it doesn't, then that isn't a reason - being lazy does minimise your costs in a small way though).

2) QA was low, again due to it cutting into profit margins.

This may actually be a business strategy as 

1) the el-cheapo market would typically be the SOHO market, where very few NICs are connected to the same link, and are typically bought one at a time.

2) if the SOHO customer does buy more than one NIC from a batch with duplicate MAC addresses, they won't work, will take one or both, or the group back to the shop, and get replacements, hopefully not from the same batch. Alternatively, because of the hassle they have just suffered, they may decide to go a bit more up market, where MACs are not duplicated. Because of the low cost, the shop will probably just assume the el-cheapo NICs were DOA, and throw them away.

With cheap, yet widely supported (eg Windows, Linux, etc) 10/100 MBps NICs costing around $15 AU / ~$8 US, it isn't surprising that people may not bother trying to find the real reason why NICs with duplicated MAC addresses don't work.

> On Tue, 19 Aug 2003, Bob Hinden wrote:
> 
> > Mark,
> >
> > >b) There have been cases where manufacturers have allocated non-unique MAC
> > >addresses. What is worse is that these duplications have apparently tended
> > >to happen within the same batch of NICs, and have been encountered when
> > >somebody goes to deploy a group of say 20 new NICs they have just bought,
> > >and encounter one or more duplications.
> >
> > Do you have any first hand experience of this happening?  I have heard the
> > story several times, but I would like to see something definitive.  I
> > wonder if it is an "internet urban myth".
> >

No :-), but I seem to remember that the person who told me about 10 years ago did.

Regards,
Mark.

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