Enabling Privacy Enhanced Addresses for IPv6
Many operating systems use the EUI-64 algorithm to generate IPv6 addresses. This algorithm derives the last 64 bits of the IPv6 address using the MAC address. Many see this as a privacy problem. The last half of your IP address will never change, and with MAC addresses being somewhat unique, the interface ID becomes close to a unique "cookie" identifying your system.
As a result, RFC3041 introduces "privacy enhanced" addresses which will change and are created by hashing the MAC address. Of course, each operating system has its own way to enable privacy enhanced addresses.
Windows 7:
You can use "netsh" to enable and configure privacy enhanced addresses. Use
netsh interface ipv6 show privacy
to query the status, and
netsh interface ipv6 set privacy state=enabled
to enable it. In my testing, privacy enhanced addresses were enabled and I wasn't actually able to disable them (a possible bug?).
OS X:
OS X uses the sysctl command to change various kernel parameters, including privacy enhanced addresses. By default, EUI-64 is used.
To enable, run
sudo sysctl -w net.inet6.ip6.use_tempaddr=1
and cycle the interfaces (ifconfig en0 down; ifconfig en0 up). However, to have this setting survive a reboot, create a file called /etc/sysctl.conf and add the line:
net.inet6.ip6.use_tempaddr=1
Linux:
as root, similar to OS X, update the respective /proc entries
echo 1 > /proc/sys/net/ipv6/conf/all/use_tempaddr echo 1 > /proc/sys/net/ipv6/conf/default/use_tempaddr echo 1 > /proc/sys/net/ipv6/conf/eth0/use_tempaddr
Linux uses an /etc/sysctl.conf file, just like OS X, to make these changes persistent during reboots.
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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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Comments
Sometimes IT admins actually do need to track down physical computers; with privacy addresses, tracking down by IP address will be complicated, since IP address changes all the time.
At least with IPv4, DHCP servers can log which MAC address had such and such IP at such and such time.
With IPv6, some new less-convenient (possibly more failure-prone) monitoring mechanism will need to be devised, to be able to track what MAC address had what privacy address and such and such time, for auditing purposes.
Mysid
Jun 1st 2011
1 decade ago
netsh interface ipv6 set privacy state=enabled
ylokiple
Jun 1st 2011
1 decade ago
Regarding corporate networks: I agree. And this was one reason why at least for Vista, the "Pro" versions had EUI-64 addresses and the "Home" versions used privacy enhanced.
Sadly, I can't get EUI-64 to work for Windows 7. (but still experimenting with it... so maybe later)
Dr. J
Jun 1st 2011
1 decade ago
http://ipv6int.net/systems/linux-ipv6.html#privacy
Jason
Jun 1st 2011
1 decade ago
Matt
Jun 2nd 2011
1 decade ago