FreeBSD kernel messages & IPv6

I have 2 problems
1.I wonder how to mute kernel messages after the kernel finish losing, I.e for example: when I change the name of a given net interface the kernel display a message indicating that changement
ifconfig em0 name pp1
The kernel in tty0 display a mesage
em0 name changed to pp1. So who to deactivate this.
2. How to disactivate IPv6 definitely without recompiling the kernel.