hi, i am disabling ipv6 with the next command: /ipv6 settings set disable-ipv6=yes, if I reboot the router, or turn it off through the winbox, everything is correct, ipv6 is turned off during next power-up.
But if an unplanned power outage occurs, ipv6 is turned on the next time router is turned on. It is not right, I disabled ipv6 for security, but any power failure turns it back on.
P.S. 7b4 on 2011UiAS-2HnD if it is important
Hey. I don’t thinjk you can really disable IPv6 via this optin you’ve wrote. There is no such command. Best option to secure your network is to use native ipv6 firewall filter.
this parameter was added in beta 4, see the changelog:
*) ipv6 - added “disable-ipv6” parameter;
and it doesn’t work correctly, this bug report about it
On CHR “disable-ipv6” setting returns to “no” even after correct shutdown or reboot.
I think it is better to disable the package, for now.
ipv6 is a part of the main system package in ROS v7
Didn’t know that. Interesting 
If you reset the router to factory defaults (or if the router is new out of the box), it will have IPv6 firewall rules by default and therefore will be secure already. Although the option is there, there should be no need to disable IPv6 entirely as a result. The only reason I can see for this option to exist is for people who are upgrading who currently have no IPv6 firewall rules.