OpenVPN bridged network without authentication

I would like to configure OpenVPN multi-client server in bridged mode(tap virtual interface). My server-side configuration is following:

dev tap0proto udpport 1194mode serverifconfig-pool 10.10.1.97 10.10.1.98 255.255.255.192management 127.0.0.1 1194auth nonelog-append /var/log/openvpn.logverb 1

Now when I start the OpenVPN server I receive the --mode server requires --tls-server error message and server does not start. Is it mandatory to use TLS with multi-client bridged mode? For example it is possible to set up point-to-point L3(tun interface) VPN's without authentication and encryption.