We have a satellite office that has about 4 voip altigen phones connected to a main office with an altigen pbx. The satellite office experiences intermittent issues where they can't hear callers on the other line but callers can hear them. This mainly happens on incoming calls. outbound seem fine. We have a juniper firewall. and i've read about disabling the SIP alg which i've done on both office (satellite and main) juniper firewalls. That didn't help either. They are using a comcast internet service which has claimed there is no firewall on their side. I've read some on the juniper website about creating a dip pool?, which i've never done and not sure i quite understand.

Does anyone have any suggestions?