Order of precedence in multiple forward-addr in unbound

[Andrew453]

Hi. I couldn't find an answer to this from Googling.

If I have the following in my unbound configuration, do each of the three upstream dns servers get used equally (load balancing style), or are they queried in sequence but only if the first server doesn't respond etc (i.e. in fail over style)?

forward-zone:
  name: "."
  forward-addr: 9.9.9.9@853
  forward-addr: 149.112.112.112@853
  forward-addr: 8.8.8.8@853

If they are effectively load balanced, is there a way of setting it up so that one or more of the upstream servers only work on a fail-over basis please?

[Andrew453]

p.s. I also checked the unbound documentation but it doesn't seem to address this particular point.

The documentation can be found here: https://nlnetlabs.nl/documentation/unbound/unbound.conf/