Babel and Unnumbered interfaces

[Juliusz Chroboczek]

> 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