Do I need disable IPv6 on CentOS 6.0? If yes, how exactly?

[TrevorH]

The ipv6 modules needs to load as many other modules are now dependent on it. If you blacklist the ipv6 module or alias it to off in /etc/modprobe.conf then you will no longer be able to load those dependent modules. For example, the one that Redhat mention in their docs is the bonding module - so you cannot bond multiple interfaces together and disable ipv6 using the old method any more. Since the sysctl stuff was backported from 6 to 5, my doubt was whether it was going to work properly on Centos 5. My initial testing was done on CentOS 6 and that's where it worked for me but 5 is all I have here.

[vdubhack]

But shouldn't I not be getting an ipv6 address in ifconfig with the sysctl.conf settings, or am I missing the point? The only thing I do is reboot start firefox and log back on here. Thank you.

[TrevorH]

So now I'm back in front of my CentOS 6 system and it definitely does not have an ipv6 address and the only thing I have done is to add those two settings to /etc/sysctl.conf. I did just check my /etc/sysconfig/network/ifcfg* files and in the one for eth0 I have NM_CONTROLLED="no" specified but that's not true for the wireless connection on the same machine and that has no ipv6 address either.

I also have a CentOS 6 x86_64 system here and have just tested on that too

[code]
# ifconfig (shows an ipv6 address on eth0 and lo)
# sysctl net.ipv6.conf.default.disable_ipv6=1
# ifconfig (shows an ipv6 address on eth0 and lo)
# sysctl net.ipv6.conf.all.disable_ipv6=1
# ifconfig (now has no ipv6 addresses on eth0 or lo)
[/code]

[vdubhack]

I think I figured out what was making it load back up and that was Firefox. Once I disabled ipv6 in about:config and then rebooted again its stayed once I started surfing. I noticed that there was no ipv6 on the fresh boot and it would only start after I loaded Firefox. But since I have done the extra tweak in Firefox it seems to be gone now. Thanks for the extra help there Trevor, I checked my ifcfg* and mine was set with 1 but I did not change that file and its has stayed persistent. I have done a few extra reboots and playing with FF since I got it. On this I am a happy camper now and thank you.

[pschaff]

I would not have expected an application run by an unprivileged user to cause IPv6 to load, but if it's fixed, it's fixed. :-)

Also just noted that a thread hijacking has occurred. In the future please start your own fresh thread, with a link to the original if required for context.

[fsck_y]

http://wiki.centos.org/FAQ/CentOS6#head-d47139912868bcb9d754441ecb6a8a10d41781df


4. How do I disable IPv6?

Upstream employee Daniel Walsh recommends not disabling the ipv6 module, as that can cause issues with SELinux and other components, but adding the following to /etc/sysctl.conf:

net.ipv6.conf.all.disable_ipv6 = 1

[pschaff]

[quote]
fsck_y wrote:
http://wiki.centos.org/FAQ/CentOS6#head-d47139912868bcb9d754441ecb6a8a10d41781df
[/quote]
Welcome to the CentOS fora. Please see the recommended reading for new users linked in my signature.

That FAQ entry was created because of this thread - back about post #8/9. Not sure what the point is in repeating it, never mind including the full text. Perhaps another consequence of the previous thread hijacking.

[r_hartman]

OT: maybe threads that have been marked resolved (this one isn't, by the way, at least not visible) or have been inactive for a certain amount of time could be locked to prevent hijacking?

[pschaff]

That is sometimes done, and I thought about locking this one during my last post, but decided it was not [b]that[/b] stale and the OP might still come back. On reflection, given we are almost three months out from the last non-hijacked post, and still no word from the OP, I will lock it. Thanks for the suggestion.