IPv6: should be enabled or disable?

[LinuxIsOne]

On Fri, Dec 9, 2011 at 9:52 AM, Avi Greenbury <lists at avi.co> wrote:

> There's generally no compelling reason to either enable it or disable
> it. You only need it enabled if you're using an IPv6 network, and the
> only reason to disable it would be because of bugs it triggers.

Oh I see. I used to think as if the disabling of IPv6 is good for
better speed in Internet. But as you say, there is no need to disable
it. But how  can I check if it enable or disable or what?