Hi Eric
> What is not clear to us is:
> 1- how can a P router, IPv4 only, generate an IPv6 icmp
message (for
> example, which source addres should it use?)
>
>
> If the router is IPv4 only, it simply cannot. However, if it has
IPv6 capability, but not IPv6 connectivity, then it is not very
different from a P router when it needs to generate an ICMP message to a
VPN destination. Does not know the destination; and does not have any
topologically valid source address. For reaching the destination, it
tunnel the icmp message in mpls. For the source, it picks one among the
one >it has, and "hope" the destination will not filter it.
> For 6PE, it's the same. The source address can be any IPv6
address in the box, and if they are none, it can be a v4-mapped IPv6
address.
>None is going to be topologically correct of course ...
We agree with you about the general behaviour of a P regarding an ICMP
(v4/v6) message to be sent back to a generic source. However, as you
say, a P node in an MPLS backcbone is not able to generate an IPv6
packet (in this case an ICMPv6). So a specific functionality is required
for the P router to generate the IPv6 packet even if IPv6 has not been
enabled (may be supported, but not enabled).
IMHO this would require, to fully support the 6PE mechanism, an upgrade
of all the P-router releases; that is exactly what i was trying to avoid
with the 6PE solution.