Configuring your firewall for voice

Allow cloudnumbering's SIP signalling and RTP media through your firewall so calls connect with audio in both directions.

Signalling

Send SIP signalling to sip.cloudnumbering.com on port 5060, over UDP. SIP over TCP or TLS is not currently supported.

• cloudnumbering does not use SIP registration. Do not send REGISTER — it is rejected. Outbound calls are authorised by your allowed source IPs instead.
• cloudnumbering answers SIP OPTIONS, so you can use OPTIONS keepalives to monitor the trunk.

Media

Call audio is RTP over UDP. On cloudnumbering's side, media uses ports 23000 to 32768 on its media servers. Allow UDP between your PBX's RTP port range and that range in both directions.

Troubleshooting

Calls connect but have one-way or no audio.

Your firewall is passing signalling but blocking media. Allow the UDP media range above in both directions and check that your PBX advertises a publicly reachable address in its SDP.

Every call is rejected.

Check the SIP response code. 418 means your source IP is not on the voice allowlist — see Troubleshooting voice calls.

Related articles

• Making outbound voice calls
• Receiving inbound voice calls
• Configuring allowed IPs
• Troubleshooting voice calls