So I have following configuration: OBi100 behind ZyWALL USG50 on Callcentric voip.
All incoming calls get "User not available" message unless I forward port 5060 to OBi.
My firewall configuration is:
Enable SIP ALG OFF
Enable SIP Transformations ON
Enable Configure SIP Inactivity Timeout ON
SIP Media Inactivity Timeout 120 secs
SIP Signaling Inactivity Timeout 1800 secs
SIP Signaling Port 5060
I would prefer not to forward port 5060 - Should I change the timeout values to something else?
Ok, I figured it out by trial and error. For ZyXEL ZyWALL USG series firewalls (firmware 3.0 and later) you have turn SIP ALG on. By default, it is off and you will not be able to receive calls. No other change (port forwarding) was necessary for me.