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Answered Wrong autoconfigured IPv6 address

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      Sunday, January 11, 2009 7:02 PM
       
       
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      I have an OpenBSD 4.4-current box at home that is configured to send IPv6 Router Advertisements (by means of the rtadvd daemon). My Mac OS X and Linux machines configure their IPv6 addresses fine, by using the prefix from the Router Advertisements plus part of their NIC MAC addresses. However, my Windows 7 machine seems not to use the NIC MAC address but some bits I can't figure out where they come from. It gets three IPv6 adddresses: link-local, IPv6 and Temporary IPv6. Looks like Windows 7 is using IPv6 privacy extensions, but what's even more surprising is that even the link-local IPv6 address does not contain any single bit from the NIC MAC address (it ends in :1494 where as the NIC MAC address ends in AA-E1). In the NIC properties, inside the IPv6 settings, I can't seem to find anything relevant. Another data point, which might be meaningless, is that the NIC is a Wireless LAN adapter: Atheros AR5008X (yes, you guessed right, this machine is a MacBook Pro).

      Are you familiar with IPv6 autoconfiguration in Windows 7 (or Windows Vista)?

      Thanks in advance.
       

    Answers

    • Tuesday, January 13, 2009 11:28 PM
       
       Answered
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      netsh interface ipv6 set global randomizeidentifiers=disabled

      This did the trick and makes the NIC get an autoconfigured IPv6 address that conforms to RFC 2464, as Mac OS X, Linux, Solaris and *BSDs do.

      Thanks for the tip, Alun.
       

    All Replies

    • Tuesday, January 13, 2009 10:43 PM
       
       Proposed Answer
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      Windows Vista and later use randomised identifiers for IPv6 addresses.
      You can configure this from the command line with the following command:
      netsh interface ipv6 set global randomizeidentifiers
      • Proposed As Answer by Alun JonesMVP Wednesday, January 14, 2009 12:14 AM
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    • Tuesday, January 13, 2009 11:18 PM
       
       
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      I want precisely the opposite effect. Randomizing the IPv6 address, by default, goes against section 4 of RFC 2464. Was this deliberately enabled by default? And if so, why?
       
    • Tuesday, January 13, 2009 11:28 PM
       
       Answered
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      netsh interface ipv6 set global randomizeidentifiers=disabled

      This did the trick and makes the NIC get an autoconfigured IPv6 address that conforms to RFC 2464, as Mac OS X, Linux, Solaris and *BSDs do.

      Thanks for the tip, Alun.
       
    • Wednesday, January 14, 2009 12:16 AM
       
       
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      My guess as to why it happens this way is that in a corporate environment, where things like IPv6 address matching MAC address might matter, you can set this at the deployment or by Group Policy. For a home environment, you probably want privacy and inability to probe a machine that connected to you once.