Check for IPv6: IPv6 appears to be enabled [ifconfig: ]. If ip6tables is installed, you should enable the csf IPv6 firewall (IPV6 in csf.conf). To disable IPv6 on RHEL/CentOS you should follow this link.Upon following the link you end up at the login screen for access.redhat.com. Even after creating an account viewing the link requires a subscription. Seems a little odd that a subscription is required to find out how to disable IPv6... So, here is how you do it:
>_ touch /etc/modprobe.d/disable-ipv6 >_ echo "options ipv6 disable=1" >> /etc/modprobe.d/disable-ipv6Note: Slightly different prior to the 5.4 update. For more information on the above see this link on the centos wiki. Its a bit more helpful than the link provided in the csf notes.