Não é possível executar ping em um sistema específico no IPv6

Question

Eu habilitei o IPv6 na minha rede, usando DHCPv6 e sub-rede fd00 :: / 64. O IP do meu servidor DHCP é fd00 :: 1: 1: 1 e não consigo efetuar o ping de alguns sistemas na minha rede.

Meu radvd.conf:

interface br0
{
    AdvSendAdvert on;
    AdvManagedFlag on;
    AdvOtherConfigFlag on;

    MinRtrAdvInterval 3;
    MaxRtrAdvInterval 60;

    prefix fd00::/64
    {
        AdvAutonomous off;
        AdvOnLink on;
    };
};

Endereços IPv6 no servidor DHCP:

# ip -6 addr list dev br0
4: br0:  mtu 1500 state UP qlen 1000
    inet6 fd00::1:1:1/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::223:5aff:fe5c:3035/64 scope link
       valid_lft forever preferred_lft forever

No cliente:

   IPv6 Address. . . . . . . . . . . : fd00::5(Preferred)
   Lease Obtained. . . . . . . . . . : 27 July 2016 19:37:38
   Lease Expires . . . . . . . . . . : 02 August 2016 22:13:23
   IPv6 Address. . . . . . . . . . . : fdf4:9ff3:68e4:3600:8c44:7b7d:8cd5:22b5(Preferred)
   Temporary IPv6 Address. . . . . . : fdf4:9ff3:68e4:3600:e10d:6a8d:d16f:ebf0(Preferred)
   Link-local IPv6 Address . . . . . : fe80::8c44:7b7d:8cd5:22b5%9(Preferred)
   IPv4 Address. . . . . . . . . . . : 10.0.0.5(Preferred)

O servidor está executando o Ubuntu 16.04.1, o cliente é o Windows 10.

Eu sou capaz de fazer ping do servidor para o cliente:

$ ping6 -w5 -c1 fd00::5
PING fd00::5(fd00::5) 56 data bytes
64 bytes from fd00::5: icmp_seq=1 ttl=64 time=0.245 ms

--- fd00::5 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.245/0.245/0.245/0.000 ms

Mas não é cliente para servidor:

>ping -n 1 fd00::1:1:1

Pinging fd00::1:1:1 with 32 bytes of data:
Request timed out.

Ping statistics for fd00::1:1:1:
    Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),

Eu posso pingar o endereço local do link embora.

O cliente pode executar ping em outros sistemas IPv6 na minha rede:

>ping -n 1 fd00::1

Pinging fd00::1 with 32 bytes of data:
Reply from fd00::1: time<1ms

Ping statistics for fd00::1:
    Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

Não está sendo bloqueado pelo iptables no servidor (as tabelas raw, mangle e nat também estão vazias com a política definida como ACCEPT):

# ip6tables -n -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Eu passei alguns dias tentando descobrir isso, mas não cheguei a lugar nenhum. Alguém tem alguma ideia?

Tabela de roteamento do Windows:

>route print -6
===========================================================================
Interface List
  9...54 04 a6 25 ea 42 ......Intel(R) 82579V Gigabit Network Connection
  4...54 04 a6 25 f2 de ......Realtek PCIe GBE Family Controller
  7...00 50 56 c0 00 01 ......VMware Virtual Ethernet Adapter for VMnet1
 10...00 50 56 c0 00 08 ......VMware Virtual Ethernet Adapter for VMnet8
  2...00 ff 27 7c db d5 ......TAP-Windows Adapter V9
  8...5c f3 70 69 f8 ad ......Bluetooth Device (Personal Area Network)
  1...........................Software Loopback Interface 1
  3...00 00 00 00 00 00 00 e0 Microsoft Teredo Tunneling Adapter
===========================================================================

IPv6 Route Table
===========================================================================
Active Routes:
 If Metric Network Destination      Gateway
  9    266 ::/0                     fe80::223:5aff:fe5c:3035
  1    306 ::1/128                  On-link
  9    266 fd00::/64                On-link
  9    266 fd00::5/128              On-link
  9     26 fdf4:9ff3:68e4:3600::/64 On-link
  9    266 fdf4:9ff3:68e4:3600:8c44:7b7d:8cd5:22b5/128
                                    On-link
  9    266 fdf4:9ff3:68e4:3600:a44b:f98d:2032:cb57/128
                                    On-link
  7    276 fe80::/64                On-link
 10    276 fe80::/64                On-link
  9    266 fe80::/64                On-link
  3    306 fe80::/64                On-link
  3    306 fe80::8d:10d8:a79e:ff1d/128
                                    On-link
  7    276 fe80::68f0:76f0:9474:d11d/128
                                    On-link
  9    266 fe80::8c44:7b7d:8cd5:22b5/128
                                    On-link
 10    276 fe80::9875:1c54:698b:b9d2/128
                                    On-link
  1    306 ff00::/8                 On-link
  7    276 ff00::/8                 On-link
 10    276 ff00::/8                 On-link
  9    266 ff00::/8                 On-link
  3    306 ff00::/8                 On-link
===========================================================================
Persistent Routes:
  None