Hi

How can i disbale ipv6 on Centos 6.6 ?

Thanks

I don't use CentOS, but I think this will work if you add it to your kernel command line parameters:

No idea how to do it

Use sysctl command to do it.

How?

It seems that Centos server 6.6 is trying to use always ipv6 (don't know why) and not ipv4

If you don't know what to look for and somebody gave you a hint then first reflex should be to use the standard local "which", "whatis", "whereis" and "locate" commands, or (the local copy of) the CentOS documentation and search LQ before resorting to using an online search engine. This is efficient. In your case the CentOS FAQ has an appropriate entry: http://wiki.centos.org/FAQ/CentOS6#h...6a8a10d41781df .

Ok thanks

Is there any other way to force all connections to use ipv4?

As if i use wget is not working for a file link and if i use wget -4 is working great for the same file link ?

That means you have not disabled IPv6 properly. (Re-)check /proc/cmdline, sysctl and /etc/sysctl.conf, (if|iw)config, lsmod, any /etc/mod*/ output / contents for anything IPv6-related.

I mean to do this with ipv6 enabled....

There are a few ways to do this (ranging from simple to complex), including:

1. Adjust network settings.
2. Use /etc/sysctl.conf to adjust /proc/sys/ kernel parameters.
3. Blacklist kernel modules associated with IPv6.

Option 1: Adjust network settings

Add/ensure "NETWORKING_IPV6=no" to /etc/sysconfig/network
Add/ensure "IPV6INIT=no" to /etc/sysconfig/network-scripts/ifcfg-eth0 or similar (depending on interface).

Option 2: Adjust /etc/sysctl.conf

Add/ensure "net.ipv6.conf.default.disable_ipv6 = 1" is in /etc/sysctl.conf
Run "sysctl -p" to apply this changed setting from /etc/sysctl.conf configuration file
Alternatively, "echo 1> /proc/sys/net/ipv6/conf/default/disable_ipv6" ... but this won't persist after reboot.