[CentOS] Kernel is not compiled with IPv6 support?

> CRITICAL : [ipv6_test] Kernel is not compiled with IPv6 support
>                                                          [  OK  ]
> FATAL: Module off not found.
> CRITICAL : [ipv6_test] Kernel is not compiled with IPv6 support

Try looking inside /etc/modprobe.conf for these lines:
alias net-pf-10 off
alias ipv6 off

If those are in there then ipv6 will be disabled at boot.