Remote STUN IP Phones usually require more configuration outside of 3CX therefore we recommend the use of the 3CX APPs in home offices, or using the 3CX SBC whenever deploying remote phones.
When this is not possible and you need to deploy phones in STUN you can follow our checklist below:
Prerequisites:
- Access to the PBX Firewall
- Access to the Remote Location Firewall
3CX Server Configuration:
- Your SIP, HTTPS, RTP ports must be open: https://www.3cx.com/docs/ports/
- Firewall checker must pass on all checks: https://www.3cx.com/docs/troubleshooting-firewall-checker/
- Edit your extension, under Options > Restrictions and disable “Disallow use of extension outside the LAN (Remote extensions using Direct SIP or STUN will be blocked)“
- Edit your extension, under Options > Troubleshooting and enable “PBX Delivers Audio“
- For each IP Phone installed at the same Remote Location, set a:
– Unique SIP port not shared with any other phone
– Unique range of RTP ports, not overlapping with any other phones
– Use our phone guides to see how to setup your specific model in Remote/RPS mode: https://www.3cx.com/sip-phones/
Remote Location Configuration:
- Assign a static IP to each phone (or use DHCP reservation)
- Port forward each phone’s unique SIP port and RTP port range on the Remote Location Firewall
- Disable any SIP ALG or SIP Helpers running on the Remote Location Firewall
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