>I have NetBSD 1.6.1RC3 installed and I noticed following behaviour in
>autoconfiguration. The autoconfigured addresses dissapears every once
>and a while for a few seconds. What I noticed was that this happens
>every time the address has been configured for a valid life time
>although the host has received a number of router advertisements during
>this time.

	the basic suggestion is, as documented in rtadvd(8), do not have
	rtadvd.conf and let rtadvd(8) determine what prefix to be advertised
	from interface configuration in the kernel.  use rtadvd.conf only when
	you are sure really about it.

>E.g. if I have configured at my IPv6 router in rtadv.conf following:
>xl0: \
>   :addrs#1:addr="2ffe:300:20:3e00::":vltime#60:pltime:30: \
>   :maxinterval#4:mininterval#3:rltime#60:

	there's a typo: pltime#30, not pltime:30.  maybe it is the cause?

itojun