Disable IPv6 in Red Hat Enterprise Linux 5
By default, RHEL kernel comes with IPv6 enabled. Since many of us don't need it, it's pointless to recompile the kernel just to disable IPv6.To disable IPv6 on RHEL 5 add the following lines in /etc/modprobe.conf:
alias net-pf-10 off
alias ipv6 off
This will require a reboot.