Do I need stun server?

[mayuqiang]

My 3cx phone system (version 3.1) and 3cx phone are located at 2 different private network. Both are behind firewall. When I add stun server (stun.3cx.com) in my 3cx phone's configration, 3cx phone failed to register. But when I remove stun server from my configration, registration succeed. Why will be like this? Whether I need stun server?

Thanks

 

[miraportuga]

If they are located at 2 diferent locations you need stun server or something that will send along with the registratio the real IP of that phone, otherwise you wont have the sound sent to the other phone....
What phone are you using? It might be a problem with stun server on the phone itself, ive seen many cases like this nowadays, works without, but with.. well...

Cheers