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An exact definition of the OpenVPN remote server protocol must be present,
Otherwise, it may try to establish a connection with the wrong version of IP protocol.

see https://redmine.pfsense.org/issues/10368

from openvpn(8):

--remote host [port] [proto]
              Remote host name or IP address.  On the client, multiple --remote options may be specified for redundancy,  each  re‐
              ferring  to  a  different OpenVPN server.  Specifying multiple --remote options for this purpose is a special case of
              the more general connection-profile feature.  See the <connection> documentation below.

              The OpenVPN client will try to connect to a server at host:port in the order specified by the list  of  --remote  op‐
              tions.

              proto indicates the protocol to use when connecting with the remote, and may be "tcp" or "udp".

              For forcing IPv4 or IPv6 connection suffix tcp or udp with 4/6 like udp4/udp6/tcp4/tcp6.