I've got IPv6 addresses from SIXXS. My host is connected with SIXXS network over a AICCU tunnel ("sixxs" interface). My host address is 2001:::2, the host on the end has address 2001:::1. On my host IPv6 is fully accessible. I have problem with configuring IPv6 network on VMs. I use VirtualBox, the VM (Ubuntu) uses tap1 (on the host bridged by br0)

#!/bin/sh

PATH=/sbin:/usr/bin:/bin:/usr/bin:/usr/sbin

# create a tap
tunctl -t tap1
ip link set up dev tap1

# create the bridge
brctl addbr br0
brctl addif br0 tap1

# set the IP address and routing
ip link set up dev br0
ip -6 route del 2001:6a0:200:172::/64 dev sixxs
ip -6 route add 2001:6a0:200:172::1 dev sixxs
ip -6 addr add 2001:6a0:200:172::2/64 dev br0
ip -6 route add 2001:6a0:200:172::2/64 dev br0

Host: routing table:

2001:6a0:200:172::1 dev sixxs  metric 1024 
2001:6a0:200:172::/64 dev br0  proto kernel  metric 256 
2001:6a0:200:172::/64 dev br0  metric 1024 
2000::/3 dev sixxs  metric 1024 
fe80::/64 dev eth0  proto kernel  metric 256 
fe80::/64 dev sixxs  proto kernel  metric 256 
fe80::/64 dev br0  proto kernel  metric 256 
fe80::/64 dev tap1  proto kernel  metric 256 
default via 2001:6a0:200:172::1 dev sixxs  metric 1024

Guest: interface eth1 (it is connected with tap1):

auto eth1
iface eth1 inet6 static
address 2001:6a0:200:172::3
netmask 64
gateway 2001:6a0:200:172::2

Guest: routing table

2001:6a0:200:172::/64 dev eth1 proto kernel metric 256
fe80::/64 dev eth0 proto kernel metric 256
fe80::/64 dev eth1 proto kernel metric 256
default via 2001:6a0:200:172::2 dev eth1 metric 1024

The guest pings to the host, the host pings to the guest, the host pings to 2001:6a0:200:172::1, but the guest doesn't ping to 2001:6a0:200:172::1. The guest tries to ping, on the host (by tcdump) I can capture its packets, but the host doesn't send them to 2001:6a0:200:172::1. What have I missed in configuration?