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 tap0
proto udp
port 1194
mode server
ifconfig-pool 10.10.1.97 10.10.1.98 255.255.255.192
management 127.0.0.1 1194
auth none
log-append /var/log/openvpn.log
verb 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.