A STUN server is required to determine the client's public IP. You can try without it, but I wouldn't recommend it.To disable the STUN server locate "turn-stun-servers.xml" (There are different locations in 2.0 and 2.2). Once you've located the file edit it and comment out the stun1 bean reference.
<bean id="stunTurnService" class="org.bigbluebutton.web.services.turn.StunTurnService">
<property name="stunServers">
<set>
<!--ref bean="stun1" /-->
<!--ref bean="stun2" /-->
And then restart bbb-web. In 2.0 it's "sudo systemctl restart tomcat7" and in 2.2 it's "sudo systemctl restart bbb-web".
Make sure you heavily test with different browsers and OSs in all network locations that you want to work (ie outside and inside your network).