Fallback lookup with changed source address

[Florian Weimer]

Suppose I have two Internet connections which can be selected by
choosing different source address (using outgoing-interface in
Unbound's terms).

What are my options for getting Unbound to use both Internet
connections for lookups before reporting failure?

Should I launch two daemons, one internal one, and one exposed to
clients?  And the latter uses a forward zone, points forward-host to
the internal daemon, and has forward-first enabled?