I've been using 3CX in the UK for several years with a Patton ISDN gateway without any problem. We have a full license with 8 simultaneous calls. The company is moving and have decided to move to full VOIP service using one of the approved 3CX partners. Our set up right now is two fibre ADSL connections going through a router/firewall to the office network. Nothing particularly clever is set up on the network, the switch ports the phones are hooked into are 802.1p priority 7 along with the 3CX server, all other ports are default priority 4. I'm not convinced this is making any difference, however it all works so haven't needed to dig further. The same switch handles all data on the network. We have been using VOIP in parallel with our legacy ISDN for several weeks, all outbound and increasingly inbound (using new phone numbers) are solely VOIP across our broadband connection. To date I've not noticed any change in call quality (which is very good), nor heard of any call drops or other issues. Staff in the office are unaware that anything has changed which clearly indicates a satisfactory service. Our new premises is yet to have fibre broadband (due late 2015) but does have high rate ADSL2, line speed is consistently above 19Mbps down, 1.1Mbps up. So, I'm wondering what is the best set up to try to ensure reliable high quality voice traffic. My thoughts follow, I'd be very grateful for any input from others who have good setups? Install another ADSL line. Possibly through the VOIP supplier to reduce network hops. Install new PoE switch, connect all SIP phones (mix of Cisco SPA and Yealink) and 3CX to this switch only. Run all phones and 3CX box on different IP subnet. Phones are configured with static IP, this has proven reliable to date. Use other ADSL feed for data, connect all office computers etc to this via a separate dedicated switch. Link the 3CX computer to data network via second LAN adapter and assign second static IP to it on the data lan subnet. Hopefully this will permit 3CX myphone clients on the data side to connect. Note we do NOT use myphone for voice traffic, purely for managing incoming calls, and sometimes for call transfers. Welcome any thoughts/ideas/problems with this config, many thanks for your time.