We are experiencing strange behavior with our VoIP phones, and I was hoping someone might be able to offer some suggestions. DISCLAIMER: my networking knowledge is very limited.
We have approximately 20 Polycom VVX 400 phones and are using 8x8 as our VoIP provider. All outgoing calls complete successfully, and most incoming calls do as well. Our issue is happening when an incoming call reaches a certain ring group. When a call comes in, it hits our "front desk" ring group. If no one answers in 3 rings, the call is transferred to another ring group consisting of 5 employees in the office. If no one answers after 3 rings in that ring group, the call is transferred to our "everyone" ring group and rings all extensions. Once the call hits this group, the call is not able to be answered either by picking up the handset or pressing the Answer soft key on the phone. It just continues to ring.
After weeks of working with 8x8 Support, I was finally passed to someone that was able to look deper and has possibly identified the issue. He told me that some phones have duplicate ports assigned, which could cause a call to be routed incorrectly or unanswerable. Now is where my lack of networking knowledge comes into play. He then asked if we were running in stealth mode as it could be why ports are shuffling so frequently and causing multiple phones to end up on the same port. When setting up the EdgeRouter, I followed the SOHO sticky, so the default is to drop all incoming packets. I assume this is essentially stealth mode. We do, however, have rules in place to open all the ports required by 8x8.
We also have NAT masquerading enabled for WAN, and the SIP ALG is disabled. Is there a way I could see which devices are using which port? Any suggestions or things to look into would be greatly appreciated.