[nsp] IPv6 in L2TP Virtual-Access interfaces

[Antoine Versini]

Dear All,

I'm currently in the process of permitting some test users to obtain
native IPv6 connection over their ADSL lines. The ADSL lines are built
this way :

CPE/PC --[PPPoE/PPPoA]--> DSLAM --[ATM]--> BAS (LAC) --[L2TP]--> LNS

The good news is : IPV6CP is working fine and link-local addresses are
exchanged. For example here is the output of a FreeBSD machine connected
with the "userland" ppp (not the kernel pppd) using PPPoE as transport
protocol :

tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1492
        inet6 fe80::201:3ff:fe41:f096%tun0 -->
fe80::250:bff:fe56:1800%tun0 prefixlen 128 scopeid 0x9
        inet 194.158.127.3 --> 194.117.192.173 netmask 0xffffffff
        Opened by PID 4199

In this case fe80::250:bff:fe56:1800 is the link-local address of the LNS,
a 7200 running 12.2(11)T. A ping from the client to the LNS' link-local is
ok. The next part is for the LNS to learn the global unicast aggregatable
address of the client using neighbor discovery (and the client to learn
the LNS' one). This is where there is a problem : it seems that the
Virtual-Template interface (and of course the Virtual-Access cloned from
that Virtual-Template) are note joining the neighbor discovery multicast
group :

Virtual-Access3 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::250:BFF:FE56:1800
...
  Global unicast address(es):
    2001:860:0:1::1, subnet is 2001:860:0:1::/64
  Joined group address(es):
    FF02::1
    FF02::2
  MTU is 1480 bytes
  ICMP error messages limited to one every 0 milliseconds
...

The interface should be in the FF02::1:FF56:1800 and FF02::1:FF00:1 groups
to learn ND advertisements.

My question is : is ND the right way to do or is there any other machanism
(setting some specific attributes using cisco av-paris in radius for
example) to exchange IPv6 global unicast addresses over a PPP connection ?

Thanks,
Best Regards,
Antoine.

-- 
Antoine Versini
IP Networks Project Manager / T-Online France - Club-Internet