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Many times you don't want to be identified while surfing. For one thing your browsing history might be sold without your knowledge, and with no benefit to you.

masegaloeh
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Fubarro
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    Related question on SuperUser: [How to avoid exposing my MAC address when using IPv6?](http://superuser.com/q/243669/1686) – user1686 May 06 '11 at 20:45

2 Answers2

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Whether or not it is a 'major concern' is a point of opinion, but this idea has been had before, and resulted in action. Microsoft itself proposed an RFC to cover just this. RFC 4941, Privacy Extensions for Stateless Address Autoconfiguration in IPv6 (Sept, 2007). IIRC, Windows defaults to use this, the Linux IPv6 stack has this as an option (your distro-of-choice may already set it by default), and OS X 10.6 also has support. That's a very large portion of end-user devices right there.

sysadmin1138
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Yes, that is a concern, and it is the reason some operating systems intentionally do not use the EUI-64 standard, preferring to use random data for the last 64 bits of their address.

Shane Madden
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  • Not entirely random though. A few of the bits are used to indicate how the address was generated. – kasperd Mar 27 '15 at 13:41