Duplicate MAC addresses

[Sam Kreimeyer]

Would it be possible that a user set their MAC to that address? This can be
done on linux machines with ifconfig.


On Thu, Feb 6, 2014 at 7:22 PM, Michael Butash <michael at butash.net> wrote:

>  Normal?  No, this goes against a lot of things networking, so definitely
> not kosher.  Two mac's in a broadcast domain is an extremely bad thing
> usually causing a switch to start flooding unicast traffic within a vlan.
> Microsoft thought this was a great way to do redundancy with Network
> Load-Balancing replicating macs among cluster members until network people
> realized it was breaking their lans (essentially turning switches into
> hubs).  I have some mega-outages I can attribute to this commonly over the
> years...
>
> Does it happen?  Sure - as chinese companies clone each other and other
> legit vendor hardware apparently eeprom data and all, not bothering to
> register an oui id themselves, I'm not entirely surprised.  Buy those $5
> ebay generic nics in bulk, i'm sure you'll start getting mac collisions.
>
> Another reason to stay with reputable sources of hardware...
>
> I'd be curious what hardware it is being cloned indiscriminately, as would
> whoever owned the rights to the registered OUI.
>
> https://www.wireshark.org/tools/oui-lookup.html
>
> -mb
>
>
>
> On 02/06/2014 04:50 PM, Daniel Stasinski wrote:
>
> The past few days I've been trying to solve a mystery.
>
> I've run a disability chat room for 17 years now and the whole time we
> have had our own custom chat client that connects to a customized
> ircd.  For the identd portion of the connect, I have always used an 8
> digit random number but as of v3 of the client, I seeded the random
> number generator with their MAC address so their identd would be the
> same if they re-installed.  I have always been under the impression
> that no two devices would ever share the same MAC.  Note that this
> isn't a security issue for the site, it's just a convenience thing for
> me.
>
> In the last couple of months, 4 people have come in with duplicate
> id's.  This has never happened before.  Finally today a new guy came
> in and he turned out to be a programmer too so we talked about it and
> he gave me his pc's mac address.  58-2c-80-13-92-63. On a whim, I
> googled it and holy crap!
>
> I'm going to switch algorithms but I'm still curious, is it normal for
> vendors to recycle MAC addresses?
>
> Daniel
>
>
>
>
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