title: Disabling IPv6 in RHEL 5.4 and Fedora 12 link: https://onemoretech.wordpress.com/2010/04/09/disabling-ipv6-in-rhel-54-and-fedora-12/ author: lembobro description: post_id: 168 created: 2010/04/09 05:37:11 created_gmt: 2010/04/09 05:37:11 comment_status: open post_name: disabling-ipv6-in-rhel-54-and-fedora-12 status: publish post_type: post

Disabling IPv6 in RHEL 5.4 and Fedora 12

You know the drill. When entering the voice mail hell that is your doctor’s PBX, you hear the familiar words, “Pay attention because the menus have changed”.

As have the rules for how to disable IPv6 support in RHEL and Fedora in versions 5.4 and 12, respectively.

(I’m not going to get into the debate over why you should disable IPv6 if you’re plugged into an IPv4-only network: it’s just too tedious to get into here.)

To disable IPv6 in RHEL 5.4:

Add the following lines to /etc/modprobe.conf:

alias net-pf-10 off options ipv6 disable=1

It is also recommended to change /etc/sysconfig/network to read:

NETWORKING_IPV6=no

Finally, be sure to prevent the IPv6 firewall from coming back up on the next reboot by doing a:

/sbin/chkconfig ip6tables off

Then reboot.

Source: Red Hat Knowledge Base, “How do I disable the IPv6 protocol in Red Hat Enterprise Linux?”

As for Fedora 12, according the the not-so-voluminous doc on the subject all you have to do is:

Create a file under /etc/modprobe.d (e.g. “blacklist-ipv6.conf”) with the following 2 lines, in the order shown:

install ipv6 /bin/true blacklist ipv6

Then make sure /etc/sysconfig/network reads as described above.

You’ll also want to turn off ip6tables and use chkconfig to keep it off as described above (chkconfig ip6tables off).

Reboot once you’re done and all should be well in the world again.

This tip courtesy of Disabling IPv6 in Fedora over on Fedora Solved.

If you run servers keep in mind that there are some common daemons that may be configured to operate both on IPv4 and IPv6. Be sure to disable their IPv6 configuration (don’t worry, if you don’t they’ll probably fail to start or even better — misbehave in difficult to decipher ways).

An amusing walk through of some of the misdirection you may get on various forums, lists and blogs is found in FAIL IPv6 support Fedora, Ubuntu et al.

Following on the heels of the latest announcement from IANA that the last block of IPv4 addresses has now been let out, you may someday want to consider re-enabling IPv6 in your systems. While IPv6 doesn’t play well in an IPv4 world, the fact that the new protocol is fast becoming dominant in fast growing areas like China means that we’re on the verge of a transition. Here are the instructions for re-enabling IPv6 for RHEL/CentOS 5 from the KB:

1. Remove the following lines from the /etc/modprobe.conf file:

alias net-pf-10 off
alias ipv6 off

2. Set the following parameter in the /etc/sysconfig/network file:

NETWORKING_IPV6=yes

3. Reboot.

Copyright 2004-2019 Phil Lembo