Using 3CX Version 11 SP4 with Polycom 450 phones, Cisco SG300 switches, Cisco ASA 5505 Firewall and cable internet with SIP connection. We were recently using a SonicWall TZ210 with no issues until it had a hardware failure. We used the ASA previous to the Sonicwall but had audio issues, now that the Sonicwall is down we needed a quick replacement and reinstalled the ASA5505. I would really like to figure this out. Outbound audio has absolutely no problems, clear audio - person on the other line can hear us just fine. Inbound audio cuts in and out sporadically like packets are missing in the audio stream. It does not matter if it was an incoming our outgoing phone call, internal calls work and a wireshark capture shows that it happens on the server NIC, so you can rule the Polycom phones out. Our internet connection is good with 100MB down and 20MB up. This happens even when there is only one person on the phone. Please let me know if you need further information. BTW, I am a newb when it comes to Cisco routers so please try not to go to far over my head. Appreciate any assistance.