Privacy Extensions as defined in RFC4941 make your device change its IP every now and then. In Ubuntu, these privacy addresses are not enabled by default. Their generation is activated via the sysctl directive use_tempaddr that can be set to one of the following values:
0 Don’t use privacy extensions.1 Generate privacy addresses2 Prefer privacy addresses and use them over the normal addresses.
You can activate privacy addresses in Ubuntu in one of two ways. You can enable it permanently by adding net.ipv6.conf.all.use_tempaddr=2 to /etc/sysctl.conf. Or enable it temporaily which will be reset on reboot:
echo 2 >/proc/sys/net/ipv6/conf/all/use_tempaddr
You can replace all with eth0 to set the value for a particular network interface.