Linux: How To Disable The IPv6 Protocol

last updated in Categories Howto, Linux, Troubleshooting

Sometime you just need to disable IPv6 protocol. In some case, you do not need it at all or it may increase browsing speed and security.

Linux has Internet Protocol Version 6 (IPv6) enabled by default, almost all distros enable it.


RHEL v4 / CentOS v4

Open your modprob.conf file (Red Hat / CentOS / Fedora and friend) and add following line:
# vi /etc/modprobe.conf

Add following line:
alias net-pf-10 off
Save and close the file. Reboot the system.
See RedHat / Centos v5.x Disable IPv6 Networking for more info.

Debian / Ubuntu Linux

If you are using Debian/Ubuntu linux (thanks to beranger), open file /etc/modprobe.d/aliases
# vi /etc/modprobe.d/aliases
Find the line:
alias net-pf-10 ipv6

Replace with:
alias net-pf-10 off
alias ipv6 off

Save and close the file. Finally, reboot the system. IPv6 support should now be disabled and it did improve my DNS performance. Also you can install DNS proxy – to improve DNS performance and squid caching server.

See Also:


Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

17 comment

  1. In Debian you should just blacklist the module like this:

    HOSTu:~# vi /etc/modprobe.d/blacklist
    ## disable IPv6 module (to avoid DNS query delays)
    blacklist ipv6

    Sometimes this works on RHEL5 too, but not always (XEN virtualization).


    1. How in the world someone would unsubscribe from your alerts?

      It feels like I made a mistake posting a comment on this forum!

  2. In Fedora, you can edit /etc/sysconfig/network and add the following:


    gksu gedit /etc/default/grub


    GRUB_CMDLINE_LINUX_DEFAULT=”ipv6.disable=1 quiet splash”

    sudo update-grub

    ip a | grep inet6

  4. Even modifying /etc/modprobe.d/aliases.conf or blacklisting ipv6 might not be sufficient. Some packages load other kernel modules that depend upon ipv6, and then it is back.

    There is only one reliable way: Build a kernel without ipv6 support.

    1. @Harri
      This is correct. I had this problem on Ubuntu I disabled ipv6 on system, however some commandline utilities were still using ipv6.

  5. You do not need to reboot the system, “sudo /etc/init.d/networking restart” should suffice (or su if sudoers is not configured to permit that).

    It may be interesting to have a tiny script or maybe two huge aliases to toggle ipv6, so whenever you stumble with something that requires it (debian multimedia repositories, for example), you may reactivate it.

    I hope the whole ipv6-and-speed get solved soon, if too many people use such circumventions, then we’ll face some trouble when everything becomes ipv6.

  6. Add these lines to “/etc/sysctl.conf” and run “sysctl -p /etc/sysctl.conf”

    #disable ipv6

    Alternatively, just run this command to disable ipv6 temporarily:

    echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6

    Aktivate again with “echo 0 ..”

    1. I like the sysctl or /proc method as it should be most reliable since some kernels may hard-code ipv6 support. If its compiled as a module then the module way will work, but its not quite as reliable.

      On the other hand, the sysctl method may not work if the module is unloaded. If the module is loaded after sysctl is processed, the config parameter may not be respected since without the module the /proc entry it wouldn’t exist yet. So use both methods if you wish to be certain.

      Since most distribution network stacks load IPv6 by default these days, the sysctl is probably the most reliable single-step. Setting the module alias to off will be useless for kernels with ipv6 hard-compiled in.

      Expert Linux server support and Security since 1996

  7. I add the following line to /etc/sysctl.conf
    net.ipv6.conf.all.disable_ipv6 = 1
    or do it for the specific nic
    net.ipv6.conf.eth0.disable_ipv6 = 1

    Then service network restart

  8. To disable ipv6 on Debian 6:
    echo net.ipv6.conf.all.disable_ipv6=1 > /etc/sysctl.d/disableipv6.conf

  9. 1. I had already made following entries in ifcfg-eth0 :
    2. Following entries were made in /etc/modprob.conf” :
    alias net-pf-10 off
    alias ipv6 off
    3. These entries in /etc/sysconfig/network :
    4. This line is added to /etc/modprobe.d/blaclist :
    blacklist ipv6
    5. Also I did one more in /etc/sysctl.conf :
    6. `net.ipv6.conf.all.autoconf = 0`
    7. `net.ipv6.conf.accept_ra = 0`

    Still I am unable to disable IPV6 on linux, any thought please

  10. Since I have been forced into this land of ozz you people call linux, how about telling us , inplain english, how does one Open your modprob.conf file (Red Hat / CentOS / Fedora and friend) and add following line:
    How do I know if I have one of these “systems”.
    why does everything has to be engineered for a Martian?
    why do I have to be a computer engineer to run this progra,

    If Windows wasn’t working directly for the NSA, I assure you I wouldn’t be here, asking questions that you people will answer with more gobble de gooK?

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