IPv4 next-hops over IPv6

[Tore Anderson]

* Jay Hanke

>     I haven't, but I cannot begin to fathom how that could possibly work.
>
>
> https://www.ietf.org/archive/id/draft-chroboczek-int-v4-via-v6-01.html
>
>
>     How can the receiving router possibly resolve an IPv4 next-hop
>     address
>     to an destination Ethernet MAC address, if the interface facing
>     the IX
>     does not have any IPv4 addresses assigned?
>
>
> A router only needs to know the l2 address to forward a frame. So 
> there would be no ipv4 address on the transitory network just an ipv6 
> that resolves to a Mac address.
>
> Kind of like ipv4 unnumbered but with ipv6 addresses on the segment. 
> Multiprotocol bgp would be used for the next hops.

In your original message you said you wanted to advertise routes *IPv4* 
next-hops over an IPv6-only IX.

The I-D you are linking to are not about that, but about advertising 
IPv4 routes with an *IPv6* next-hop. That is the exact opposite of what 
you asked about.

Advertising IPv6 next-hops over an IPv6-only IX is of course completely 
unproblematic, since the destination MAC address can then be resolved 
with standard ICMPv6 ND.

Advertising IPv4 prefixes with IPv6 next-hops is also entirely 
unproblematic, assuming the routers involved support extended next-hop 
encoding (RFC 5549/8950).

What you did ask about initially, though, that is, using IPv4 next-hops 
across an IPv6-only IX, does seem impossible to me.

Tore