[6bone] Building FreeBSD ipv6 router problem

[ferryas@cc.saga-u.ac.jp (ferry astika saputra)]

I want to make some eksperiment with ipv6. I have already get my
 ipv6 address , here my ipv6 address allocation from my uplink: 
3ffe:517:30a:5800:: /64. And my topology :
		-- ---------
---------------| Router　　　|--------------|
           fxp1 ------------fxp0
Uplink	    Router: FreeBSD   Client: WindowsXP(ipv6 ready)

		4.6


Firt step I try to connet my uplink, and its succed. I can ping6
 some ipv6 site like www.kame.net, www.jp.freebsd.org.
Then I modify my rc.conf :

ipv6_enable="YES"
ipv6_network_interfaces="fxp0 fxp1"
ipv6_defaultrouter="3ffe:517:30a:5800::1%fxp1"
ipv6_gateway_enable="YES"
ipv6_router_enable="YES"
ipv6_ifconfig_fxp0="3ffe:517:30a:5880::1 prefixlen 64 up"
rtadvd_enable="YES"
rtadvd_interfaces="fxp0"

With this configuration my router can advertise to downlink, but
 cannot receive router advertisement from uplink.
Somebody can help me ?

--
ferry astika saputra
ferryas@cc.saga-u.ac.jp