2025
Otus - IPv6 for Network Engeneers 0:00 of 3:24:51
    https://www.youtube.com/watch?v=u5oX92o62Cg
2023
https://habr.com/ru/articles/782634/
https://habr.com/ru/companies/ruvds/articles/761138/
https://habr.com/ru/companies/ruvds/articles/760338/
https://habr.com/ru/articles/773708/
2021
https://habr.com/ru/company/ruvds/blog/582100/
2018
https://habr.com/company/1cloud/blog/419405/
2009
https://habr.com/ru/articles/53625/

checking
    ip a | grep inet6
    cat /proc/sys/net/ipv6/conf/*/disable_ipv6
disabling
    https://idroot.us/disable-ipv6-fedora-39/
    https://linuxconfig.org/how-to-disable-ipv6-on-linux

    sudo vi /etc/sysctl.d/90-disable_ipv6.conf
        net.ipv6.conf.all.disable_ipv6 = 1
        net.ipv6.conf.default.disable_ipv6 = 1
        net.ipv6.conf.lo.disable_ipv6 = 1
    # /etc/sysctl.conf
    sudo sysctl -p

    sudo vi /etc/default/grub
        ...
        GRUB_CMDLINE_LINUX_DEFAULT="quiet ipv6.disable=1"

    $ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
    $ ls /proc/sys/net/ipv6/
    ls: cannot access '/proc/sys/net/ipv6/': No such file or directory