IPv4 next-hops over IPv6

[Jay Hanke]

I mistyped. Should be IPv6 hops for IPv4 routes.

On Tue, Apr 23, 2024 at 9:10 AM Tore Anderson <tore at fud.no> wrote:
>
> * 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
>