RFC8950: Announce IPv4 with an IPv6 next-hop

For the last few days I have been playing with RFC8950 setup, which allows routing of IPv4 on top of IPv6. While logically it’s quite simple, it has a very powerful application towards making “IPv4 an optional” feature riding on top of an IPv6 network (but without any tunnels!)

Some of the interesting use cases:

  1. A large network can run IPv6 only everywhere on its core and leave IPv4 only on edge devices. This can work without customers doing any tweaking at their end. They still do things the old way but Backbone can run IPv6 only at its core.
  2. An IP transit backbone can run IPv6 only while exchanging IPv4 routes with its customers/peers/upstream over IPv6 sessions. So IPv4 as a “feature” stays but the network in itself is IPv6 only without the overhead of IPv4 interface config, BGP session config, firewall config, etc.
  3. An IXP can offer services without IPv4 essentually by using a (unique) IPv6 at the IX LAN & running route server to exchange both IPv4 & IPv6 routes over the IPv6 only session.