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.

If your firewall cannot use hostname rules, allow the address the hostname resolves to. sip.cloudnumbering.com currently resolves to:

• 13.42.143.121

Note: This address can change without notice. Use the hostname in firewall rules wherever your firewall supports it, and re-check the address if calls stop connecting.

• 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 these media servers:

• 178.128.164.100
• 188.166.149.80
• 188.166.171.119

Allow UDP between your PBX's RTP port range and those addresses and ports in both directions.

Note: Media addresses can change without notice. If calls lose audio after previously working, check this article for the current list.

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 .

Calls worked, then stopped, and your firewall rule uses the IP address rather than the hostname.

Check whether sip.cloudnumbering.com still resolves to the address in your rule, and update the rule if it has changed.

Related articles

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