> I don't think it's a violation of the Babel protocol to use IPv6 next hops > when > an IPv4 address is present.
Yes, it's legal, but discouraged. Please see RFC 9229 Section 2.1: If the outgoing interface has been assigned an IPv4 address, then, in the interest of maximising compatibility with existing routers, the sender SHOULD prefer an ordinary IPv4 announcement; even in that case, however, it MAY send a v4-via-v6 announcement. -- Juliusz
