Just a brief side-note for CentOS’ /etc/sysconfig/network-scripts/ifcfg-device IPV6_DEFAULTGW parameter – it does not accept the prefixlen suffix, like the DNS, or IPV6ADDR parameters! In other words, if you do put there something like “/64” (presumably) suffix at the end of your address in IPV6_DEFAULTGW parameter, the
netstat -rn -A inet6
will not display the IPv6 gateway, telling you that the system will not know how to reach the ipv6 Internet.
Not too intuitive, if you ask me but that is what it is…