interfaces

# HOST
iface eth0 inet6 static
        address  2a01:affe:affe:affe::2
        netmask  128
        gateway  fe80::1
        up sysctl -p

iface vmbr0 inet6 static
        address  2a01:affe:affe:affe::2
        netmask  64
        up ip -6 route add 2a01:affe:affe:affe::/64 dev vmbr0

iface vmbr1 inet6 static
        address  2a01:affe:affe:affe:2::2
        netmask  64
        up ip -6 route add 2a01:affe:affe:affe:2::/64 dev vmbr1


# VM vmbr0
$ ip route get 2a00:1450:4001:81c::200e
2a00:1450:4001:81c::200e from :: via 2a01:affe:affe:affe::2 dev eth0 src 2a01:affe:affe:affe::111 metric 1024 pref medium

$ ping6 -c1 2a01:affe:affe:affe::2
PING 2a01:affe:affe:affe::2(2a01:affe:affe:affe::2) 56 data bytes
64 bytes from 2a01:affe:affe:affe::2: icmp_seq=1 ttl=64 time=0.041 ms

--- 2a01:affe:affe:affe::2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.041/0.041/0.041/0.000 ms

$ ping6 -c1 2a00:1450:4001:81c::200e
PING 2a00:1450:4001:81c::200e(2a00:1450:4001:81c::200e) 56 data bytes
64 bytes from 2a00:1450:4001:81c::200e: icmp_seq=1 ttl=117 time=5.06 ms

--- 2a00:1450:4001:81c::200e ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 5.060/5.060/5.060/0.000 ms

# VM vmbr1
$ ip route get 2a00:1450:4001:81c::200e
2a00:1450:4001:81c::200e from :: via 2a01:affe:affe:affe:2::2 dev eth0 src 2a01:affe:affe:affe:2::101 metric 1024 pref medium

$ ping6 -c1 2a01:affe:affe:affe:2::2
PING 2a01:affe:affe:affe:2::2(2a01:affe:affe:affe:2::2) 56 data bytes
64 bytes from 2a01:affe:affe:affe:2::2: icmp_seq=1 ttl=64 time=0.049 ms

--- 2a01:affe:affe:affe:2::2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.049/0.049/0.049/0.000 ms

$ ping6 -c1 2a00:1450:4001:81c::200e
PING 2a00:1450:4001:81c::200e(2a00:1450:4001:81c::200e) 56 data bytes

--- 2a00:1450:4001:81c::200e ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms