@sp6mr @M0YNG The phone has been provisioned now. Don't have the time to test it at the moment but will try to call someone tonight. You are right, it's a monster space-wise but wasn't too expensive. I paid 29€ for the SPA525G2

@M0YNG Hm. My phone seems to be fully configured, I hear a dial tone, can call echo service and the speaking clock service but I won't hear a thing after being connected. Any idea what the problem might be?

@DL6MHC check your port forwarding.

SIP needs
5060 - for initial setup of the call (sounds like this is working)
10000 to 20000 for the audio, one randomly selected port for outgoing, and one for incoming.

If your router, firewall, etc. isn't forwarding these ports to your phone you will probably get silence, but others might hear you.

@M0YNG Thank you very much. I will look into it. Since I' m double NATing there's a lot of failure potential...

@DL6MHC yup, that sounds like a highly likely failure cause

@M0YNG I finally managed to get rid of double NAT by enabling bridge mode on my provider's modem/router. The phone is perfectly working now without any NAT rules through my internet exposed #Mikrotik router behind the provider hardware.

@DL6MHC 302 is the most commonly "hung out in" conference room btw

@M0YNG Thank you - will try to call in there in about an hour or so

@M0YNG if you could spare some time, it would be great trying to call me again. Wasn't in the shack when you tried yesterday

@DL6MHC sure. When are you likely to be in the shack?

@M0YNG now :)