On 3/10/2016 4:32 AM, [email protected] wrote:
Thank you very much for your comments, Eric.
Yes, RFC5549 does specify the procedures for creating a route with
IPv4 or VPN-IPv4 NLRI and an IPv6 next hop. IPv4 NLRI with IPv6 next
hop is for the situation where an IPv6-only network conneting
IPv4-only islands. VPN-IPv4 NLRI with IPv6 next hop is for the 4vPE
situation.
What I want to solve is the 4PE situation, where an IPv6-only network
running with MPLS connecting the IPv4-only islands. The routes in the
4PE NLRI have labels assigned by the 4PE routers.
RFC 5549 will work when the IPv6-only network runs MPLS.
If you want the 4PE routers to send labeled IPv4 routes to each other,
they just need to use SAFI 4.
If the core runs only IPv6/MPLS, and the next hop of a 4PE route is an
IPv4 address, I don't really see how the next hop resolution is going to
work, as the next hop (a v4 address) will not appear to be reachable
through the v6 core.
I think your proposal really is intended to treat the v6 address in the
NLRI as the next hop. But that leaves open the question of why you want
to put the next hop address in the NLRI field instead of in the next hop
field.
Besides, 4PE routers need both IPv4 next hop and IPv6 next hop to
build their IPv4 routing table and IPv6 routing table respectively.
Some people think it's a bad idea for the prefix and the next hop to be
of different address families; those folks tend to regard RFC 5549 as a
bad solution.
However, I don't see what advantage your proposal has over RFC 5549.
In order to determine whether a given 4PE route is feasible, or whether
it is the bestpath, you still have to resolve the IPv6 next hop, you
still have to consider the IGP distance to the IPv6 next hop, etc.
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