Thanks for writing this down! Wonder what it would take for a host to do router discovery using a different AF. Achieving the equivalent of "ip route add 0.0.0.0/0 via inet6 fe80::1 dev eth0”
O. > On 22 Jan 2024, at 15:39, Warren Kumari <war...@kumari.net> wrote: > > Hi there all, > > I discovered that I'd somehow misnamed a draft that Juliusz Chroboczek , Toke > Høiland-Jørgensen, and myself had written — somehow I'd managed to name it > draft-chroboczek-int-v4-via-v6, instead of draft-chroboczek-intarea-v4-via-v6. > > Anyway, it is targeted at intarea, and so I renamed and submitted it, so that > it will now actually show up in the IntArea list of documents… > > The document proposes "v4-via-v6" routing, a technique that uses IPv6 > next-hop addresses for routing IPv4 packets, thus making it possible to route > IPv4 packets across a network where routers have not been assigned IPv4 > addresses. > > This isn't yet another "let's rewrite part of the header and override some > bits", nor some new protocol / tunneling thing. It simply notes that routers > only need to determine the outgoing interface (and usually MAC address) for a > packet, and so it's perfectly acceptable for the next-hop for e.g > 192.0.2.0/24 to be e.g 2001:db8::2342. The router don't care… > > While this may be initially surprising to many people, it's actually nothing > "special", nor really groundbreaking - it's just how IP routing works. > However, because it is surprising, it is not getting widely used — and that > means that many interfaces need IPv4 addresses where they otherwise would > not. > > In fact, this functionality is already supported in (at least!): > Arista EOS (since EOS-4.30.1) > The Babel protocol > Linux (since kernel version 5.2) > Mikrotik RouterOS (since before 7.11beta2) > and the BGP protocol (see RFC8950 - "Advertising IPv4 Network Layer > Reachability Information (NLRI) with an IPv6 Next Hop"). > > So, if this already works, why are we writing a document?! > > A few reasons, including: > 1: This behavior / capability is surprising to many people - this means that > people are "forced" to use IPv4 addresses where they otherwise would not. > > 2: There should be an easy way to reference this type of behaviour/deployment > - the genesis of this document that Babel supports this (RFC9229 - "IPv4 > Routes with an IPv6 Next Hop in the Babel Routing Protocol"), but had to > describe the behavior because there was nothing to point at. > > 2: A large number of implementations don't currently support it (or, at > least, the tooling / CLI / UI doesn't allow configurations like the above). > > 3: There are some unsettled questions around the ICMP behavior — e.g: if a > router has to send an ICMP packet too big, and it doesn't have an IPv4 > address, what should it do? > > We'd really appreciate review and feedback — again, this isn't documenting a > major "change", but more noting this the design of command lines, tooling, > etc should allow it. > > W > > _______________________________________________ > Int-area mailing list > Int-area@ietf.org > https://www.ietf.org/mailman/listinfo/int-area _______________________________________________ Int-area mailing list Int-area@ietf.org https://www.ietf.org/mailman/listinfo/int-area
