Completely disable IPv6 in CentOS6
All of these are fun and good, but none really disables ipv6. You really are concerned with your NICs not being configured for IPv6, but if you really want to disable ipv6… well… disable ipv6:
In /etc/grub.conf edit the kernel lines to include:
The “trick” here, as described by TrevorH1 in #linux, is that programs can still load the module as they wish. You can check this by running lsmod or modprobe -l, you will still see the ipv6.ko kernel module. This allows user mode programs to access the kernel module in their code (so they don’t crash); but as far as the kernel is concerned ipv6.disable=1, so the kernel doesn’t really allow much to get through it.
And that’s it. IPv6 is disabled on your box… but if you want to disable a variety of fun things that you might find when seeking to disable IPv6…
In /etc/sysctl.conf change/create entries:
net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1
In /etc/sysconfig/network change/create entries:
In /etc/modprobe.d/blacklist.conf change/create entries:
blacklist net-pf-10 blacklist ipv6
Disable iptables for IPv6:
service ip6tables stop chkconfig ip6tables off
Disable ipv6 completely:
echo "install ipv6 /bin/true" > /etc/modprobe.d/ipv6_disabled.conf
With much reference:
- Scott Pack’s answer
- CentOS6 FAQ: How do I disable IPv6?
- How to Disable IPv6 in Fedora and CentOS
- TrevorH1 in #centos-social.