IPv6 is enabled by default on most Linux distros. However, IPv6 is not used most of time (at least in my case). This post introduces how to disable IPv6 support on Linux (newer Kernel versions, such as in Fedora 17).
IPv6 on Linux can be easily configured via sysctrl.
Add these lines to /etc/sysctl.conf:
Note that you will need to restart Linux to make it take effect.