[NetBSD4.0(i386)]why NetBSD did not send link-local NS when NetBSD rebooted

[wang_jiabo]

Hello, all:
   could you tell me why NetBSD did not send link-local NS when NetBSD 
rebooted.
I add ip6mode=autohost in /etc/rc.conf and add up in ifconfig.<IF> file
thanks
jiabo