[WORKAROUND FOUND] - Ipv6 with pppoe PD: RA missing?

RouterOS General
1

Activated ipv6 (dual stack) on a RB751U-2HnD with ROS 6.38.5, using IPv6 PD over PPP (my ISP, TIM in Italy, offers a dynamic ipv6 /64 prefix on pppoe).
It runs flawlessy with Windows (7 and 10), Android, iOS and linux client. On LAN and Wi-Fi (wi-fi is bridged with lan). http://test-ipv6.com/ runs with 10/10 on all client.
The problem arise if I put down and up the pppoe interface. The ipv6 prefix is renewed, but the windows client (I tried on Windows 7) doesn’t work anymore on ipv6.
The Windows client has the new prefix ipv6 addresses, plus the old prefix ipv6 addresses. All the addresses are “preferred”, and Windows chooses the old prefix ipv6 address as source address for ipv6 traffic (recorded with Wireshark). So the traffic is forwarded with the “invalid” source address but there isn’t more the return path.
I consulted some books (IPv6 Essentials and other) and searched on forum, and realized that, when a prefix become invalid (and when i disable the pppoe interface I can see the prefix as invalid on Mikrotik gui), the router must invalidate the IP by sending a RA with a lifetime of 0 for the public prefix.
I checked with Wireshark (and IPv6 firewall temporary disabled), but there is non RA with lifetime=0 for the invalid prefix, I could only capture the RA for the new prefix when I restart the pppoe interface.
The only workaround is to shut down and up the lan interface of the client (or disconnecting the cable).

Do you think that it is a bug (or feature missing) of ROS, or I’m missing some configuration?
I worked on this about a week, before posting.

This is the client IP config and ipv6 routing table before the pppoe flap:

C:\Users\Supersonia>ipconfig /all

Configurazione IP di Windows

   Nome host . . . . . . . . . . . . . . : Sonia-PC
   Suffisso DNS primario . . . . . . . . :
   Tipo nodo . . . . . . . . . . . . . . : Ibrido
   Routing IP abilitato. . . . . . . . . : No
   Proxy WINS abilitato . . . . . . . .  : No

Scheda LAN wireless Connessione rete wireless:

   Stato supporto. . . . . . . . . . . . : Supporto disconnesso
   Suffisso DNS specifico per connessione:
   Descrizione . . . . . . . . . . . . . : Intel(R) WiFi Link 5100 AGN
   Indirizzo fisico. . . . . . . . . . . : xx-xx-xx-xx-xx-xx
   DHCP abilitato. . . . . . . . . . . . : No
   Configurazione automatica abilitata   : Sì

Scheda Ethernet Connessione alla rete locale (LAN):

   Suffisso DNS specifico per connessione:
   Descrizione . . . . . . . . . . . . . : Gigabit Ethernet Broadcom NetLink (TM)
   Indirizzo fisico. . . . . . . . . . . : xx-xx-xx-xx-xx-xx
   DHCP abilitato. . . . . . . . . . . . : Sì
   Configurazione automatica abilitata   : Sì
   Indirizzo IPv6 . . . . . . . . . . . . . . . . . : 2a01:2000:2001:a0b2:6db8:5bbf:3eb3:e6e6(Preferenziale)
   Indirizzo IPv6 temporaneo. . . . . . . . . . . . : 2a01:2000:2001:a0b2:b443:4bec:8fdd:746a(Preferenziale)
   Indirizzo IPv6 locale rispetto al collegamento . : fe80::6db8:5bbf:3eb3:e6e6%10(Preferenziale)
   Indirizzo IPv4. . . . . . . . . . . . : 192.168.88.50(Preferenziale)
   Subnet mask . . . . . . . . . . . . . : 255.255.255.0
   Lease ottenuto. . . . . . . . . . . . : domenica 19 marzo 2017 09:46:52
   Scadenza lease . . . . . . . . . . .  : domenica 19 marzo 2017 16:59:05
   Gateway predefinito . . . . . . . . . : fe80::d6ca:6dff:fe27:2baf%10
                                           192.168.88.1
   Server DHCP . . . . . . . . . . . . . : 192.168.88.1
   IAID DHCPv6 . . . . . . . . . . . : 234890937
   DUID Client DHCPv6. . . . . . . . : xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx

   Server DNS . . . . . . . . . . . . .  : 2001:4860:4860::8888
                                           2001:4860:4860::8844
                                           192.168.88.1
                                           208.67.222.222
                                           208.67.220.220
   NetBIOS su TCP/IP . . . . . . . . . . : Attivato

C:\Users\Supersonia>
.......................
IPv6 Tabella route
===========================================================================
Route attive:
 Interf Metrica Rete Destinazione      Gateway
 10    276 ::/0                     fe80::d6ca:6dff:fe27:2baf
  1    306 ::1/128                  On-link
 10     28 2a01:2000:2001:a0b2::/64 On-link
 10    276 2a01:2000:2001:a0b2:6db8:5bbf:3eb3:e6e6/128        On-link
 10    276 2a01:2000:2001:a0b2:b443:4bec:8fdd:746a/128        On-link
 10    276 fe80::/64                On-link
 10    276 fe80::6db8:5bbf:3eb3:e6e6/128                      On-link
  1    306 ff00::/8                 On-link
 10    276 ff00::/8                 On-link
===========================================================================
Route permanenti:
  Nessuna

C:\Users\Supersonia>

This is the client IP config and ipv6 routing table after the pppoe flap:

C:\Users\Supersonia>ipconfig /all

Configurazione IP di Windows

   Nome host . . . . . . . . . . . . . . : Sonia-PC
   Suffisso DNS primario . . . . . . . . :
   Tipo nodo . . . . . . . . . . . . . . : Ibrido
   Routing IP abilitato. . . . . . . . . : No
   Proxy WINS abilitato . . . . . . . .  : No

Scheda LAN wireless Connessione rete wireless:

   Stato supporto. . . . . . . . . . . . : Supporto disconnesso
   Suffisso DNS specifico per connessione:
   Descrizione . . . . . . . . . . . . . : Intel(R) WiFi Link 5100 AGN
   Indirizzo fisico. . . . . . . . . . . : xx-xx-xx-xx-xx-xx
   DHCP abilitato. . . . . . . . . . . . : No
   Configurazione automatica abilitata   : Sì

Scheda Ethernet Connessione alla rete locale (LAN):

   Suffisso DNS specifico per connessione:
   Descrizione . . . . . . . . . . . . . : Gigabit Ethernet Broadcom NetLink (TM
)
   Indirizzo fisico. . . . . . . . . . . : xx-xx-xx-xx-xx-xx
   DHCP abilitato. . . . . . . . . . . . : Sì
   Configurazione automatica abilitata   : Sì
   Indirizzo IPv6 . . . . . . . . . . . . . . . . . : 2a01:2000:2001:a0b2:6db8:5bbf:3eb3:e6e6(Preferenziale)
   Indirizzo IPv6 . . . . . . . . . . . . . . . . . : 2a01:2000:2001:a17e:6db8:5bbf:3eb3:e6e6(Preferenziale)
   Indirizzo IPv6 temporaneo. . . . . . . . . . . . : 2a01:2000:2001:a0b2:b443:4bec:8fdd:746a(Preferenziale)
   Indirizzo IPv6 temporaneo. . . . . . . . . . . . : 2a01:2000:2001:a17e:b443:4bec:8fdd:746a(Preferenziale)
   Indirizzo IPv6 locale rispetto al collegamento . : fe80::6db8:5bbf:3eb3:e6e6%10(Preferenziale)
   Indirizzo IPv4. . . . . . . . . . . . : 192.168.88.50(Preferenziale)
   Subnet mask . . . . . . . . . . . . . : 255.255.255.0
   Lease ottenuto. . . . . . . . . . . . : domenica 19 marzo 2017 09:46:52
   Scadenza lease . . . . . . . . . . .  : domenica 19 marzo 2017 17:04:05
   Gateway predefinito . . . . . . . . . : fe80::d6ca:6dff:fe27:2baf%10
                                           192.168.88.1
   Server DHCP . . . . . . . . . . . . . : 192.168.88.1
   IAID DHCPv6 . . . . . . . . . . . : 234890937
   DUID Client DHCPv6. . . . . . . . : xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx-xx

   Server DNS . . . . . . . . . . . . .  : 2001:4860:4860::8888
                                           2001:4860:4860::8844
                                           192.168.88.1
                                           208.67.222.222
                                           208.67.220.220
   NetBIOS su TCP/IP . . . . . . . . . . : Attivato

C:\Users\Supersonia>route print
...........

IPv6 Tabella route
===========================================================================
Route attive:
 Interf Metrica Rete Destinazione      Gateway
 10    276 ::/0                     fe80::d6ca:6dff:fe27:2baf
  1    306 ::1/128                  On-link
 10     28 2a01:2000:2001:a0b2::/64 On-link
 10    276 2a01:2000:2001:a0b2:6db8:5bbf:3eb3:e6e6/128          On-link
 10    276 2a01:2000:2001:a0b2:b443:4bec:8fdd:746a/128          On-link
 10     28 2a01:2000:2001:a17e::/64 On-link
 10    276 2a01:2000:2001:a17e:6db8:5bbf:3eb3:e6e6/128          On-link
 10    276 2a01:2000:2001:a17e:b443:4bec:8fdd:746a/128          On-link
 10    276 fe80::/64                On-link
 10    276 fe80::6db8:5bbf:3eb3:e6e6/128                        On-link
  1    306 ff00::/8                 On-link
 10    276 ff00::/8                 On-link
===========================================================================
Route permanenti:
  Nessuna

C:\Users\Supersonia>
IPv6 is not advertising (over PPPoE)
2

After a lot of reading and testing I found that the problem is that RFC 7084 is unsupported, and so when the prefix disappears no RA is generated to obsolete old addresses.
See also http://forum.mikrotik.com/t/basic-feature-request-implementing-of-basic-requirements-according-to-rfc7084/99527/1
I found a workaround. The default “valid-lifetime” and “preferred-lifetime” for prefix are 30d and 7d. I reduced to 90s:

[admin@MikroTik] /ipv6 nd> prefix default print
          autonomous: yes
      valid-lifetime: 1m30s
  preferred-lifetime: 1m30s
[admin@MikroTik]

and reduced consequently the “ra-interval” to a value below “preferred-lifetime”:

[admin@MikroTik] /ipv6 nd> print
Flags: X - disabled, I - invalid, * - default 
 0  * interface=bridge ra-interval=30s-1m20s ra-delay=3s mtu=unspecified reachable-time=unspecified 
      retransmit-interval=unspecified ra-lifetime=30m hop-limit=unspecified advertise-mac-address=yes 
      advertise-dns=yes managed-address-configuration=no other-configuration=yes 
[admin@MikroTik]

Now, when the prefix change, the addresses are renewed whitin 90 seconds.
And this delay is adjustable, as explained.

Waiting the Mikrotik implementation of RFC 7084, I think this is the best feasible workaround.

I’ll be grateful for every info about RFC 7084 support on RouterOS. Thankyou !!!

IPv6 prefix change breaks connectivity: RA lifetime issue