>> 	Now I see.  Routers cannot be autoconfigured.  you need to perform
>> 	ifconfig by hand.
>Why is this? 
>If I run "rtsol ne0" manually after starting "rtadvd ne0", it works just
>fine. It's only /etc/rc that prevents me from doing so, and I don't know
>why.

	No, please don't do that.  I introduced "ip6mode" restriction with
	good reason.  Please do not try to trick it.

	The IPv6 specification clearly separates routers and hosts.
	Only hosts are supposed to be autoconfigured.
	The specification prohibits autoconfiguration of routers.
	This leaves us only 3 valid configuration:
						forwarding	accept_rtadv
		router				1		0
		autoconfigured host		0		1
		manually-configured host	0		0

	If you tweak sysctl setting and set both "forwarding" and
	"accpet_rtadv", unexpected behavior will result.
	Also, the spec talks nothing about the following cases (which are
	still valid, but not really well-defined):
	- autoconfigured host with multiple external interfaces
	- manually configured host with multiple external interfaces

	If you have time sys/netinet6/IMPLEMENTATION can also help you.
	I tried to put as many warnings as I could, in manpage for rc.conf
	and sysctl and some other places.

itojun