Linux: How To Disable The IPv6 Protocol

by on September 12, 2006 · 17 comments· LAST UPDATED January 10, 2010

in , ,

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.

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{ 17 comments… read them below or add one }

1 Teodor July 22, 2009 at 6:24 am

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).

Cheers

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2 Teodor October 30, 2013 at 1:30 pm

How in the world someone would unsubscribe from your alerts?

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

Reply

3 nixCraft October 30, 2013 at 6:10 pm

Check the bottom of this page or email. FYI, I just removed you from this FAQ/page.

HTH

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4 Axel August 4, 2009 at 6:35 pm

in Debian Sid it’s /etc/modprobe.d/blacklist.conf
Regards, Axel

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5 Pete August 11, 2009 at 11:29 pm

In Fedora, you can edit /etc/sysconfig/network and add the following:
NETWORKING_IPV6=no
IPV6INIT=no

Pete.

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6 Sean November 28, 2009 at 9:45 pm

DISABLE IPV6 IN UBUNTU 9.10
gksu gedit /etc/default/grub

CHANGE THIS LINE:
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”

TO
GRUB_CMDLINE_LINUX_DEFAULT=”ipv6.disable=1 quiet splash”

THEN UPDATE GRUB:
sudo update-grub

TO TEST WITH TERMINAL:
ip a | grep inet6

Reply

7 Harri January 20, 2010 at 9:02 am

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.

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8 Peter July 25, 2010 at 7:18 pm

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

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9 the dsc January 30, 2010 at 4:41 am

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.

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10 Geir Helland April 6, 2010 at 9:30 am

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

#disable ipv6
net.ipv6.conf.all.disable_ipv6=1

Alternatively, just run this command to disable ipv6 temporarily:

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

Aktivate again with “echo 0 ..”

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11 Heinrich October 24, 2010 at 11:06 am

Thanks Geir, very useful

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12 Stefan Lasiewski September 26, 2011 at 10:59 pm

I see many solutions in this thread. What are the advantages/disadvantages of doing this via /etc/modprobe.d/* [1], vs. /etc/sysctl.conf vs. /etc/sysconfig/network vs. /etc/default/grub ?

Which way is the “best” way?

[1] Also see http://tldp.org/HOWTO/html_single/Linux+IPv6-HOWTO/#AEN734 , which agrees with Vivek’s solution.

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13 Eric Wheeler January 20, 2013 at 12:37 am

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.

-Eric
Expert Linux server support and Security since 1996

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14 Thron December 1, 2011 at 8:01 pm

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

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15 Rajarshi May 19, 2012 at 6:46 am

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

Reply

16 IgnitedMind April 5, 2013 at 10:03 am

1. I had already made following entries in ifcfg-eth0 :
IPv6INIT=NO
IPV6AUTOCONF=NO
2. Following entries were made in /etc/modprob.conf” :
alias net-pf-10 off
alias ipv6 off
3. These entries in /etc/sysconfig/network :
IPV6INIT=NO
NETWORKING_IPV6=NO
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

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17 me October 16, 2013 at 4:25 pm

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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