Clearing cPHulk blocks encounters errors if IPv6 is broken, disabled, or not supported by the kernel. Here is an example of trying to an error with ip6tables:
[iptables] /sbin/ip6tables --list-rules cphulk failed: ip6tables v1.4.7:
can't initialize ip6tables table `filter': Address family not supported by protocol
Perhaps ip6tables or your kernel needs to be upgraded. :
The subprocess reported error number 3 when it ended.
at /usr/local/cpanel/Cpanel/IpTables.pm line 416.
These errors are typically caused by a broken IPv6 configuration, IPv6 being disabled, or IPv6 not being supported by the kernel.
1. You can try running the following command in case the IPv6 configuration on the server may be broken:
2. IPv6 may also not be supported by your existing version of the kernel. You can check to see if the kernel needs updates by using the following command:
yum check-update kernel
If it is determined that the kernel has an update available, you can update the kernel using yum update:
yum update kernel
You will then need to reboot the server to complete the kernel update.
3. You may need to enable IPv6 on the server. For assistance enabling IPv6, you will need to contact your hosting provider or system administrator. If you do not have a system administrator, you may find one in our listings here:
You can also find additional steps for troubleshooting IPv6 configuration issues here: