Hosts, credentials and signalling
| Setting | Sipflex value |
|---|---|
| SIP registrar / proxy | sip.sipflex.co.uk |
| SIP registration username | The Sipflex phone number or username shown in the portal |
| SIP password | The separate trunk password |
| UDP / TCP SIP | Ports 5060 or 50600 |
| TLS SIP | TCP port 5061 |
| IAX2 host | iax.sipflex.co.uk |
| IAX2 port | UDP 4569 |
| Sipflex source / peer | 52.56.188.70/32 |
Media and DTMF
| Setting | Supported or recommended value |
|---|---|
| Audio codecs | G.711 A-law (PCMA), G.711 µ-law (PCMU), G.722 and G.729a |
| Preferred simple test codec | G.711 A-law |
| Packet time | 20 ms; 10 ms is not supported |
| DTMF | RFC2833 / RFC4733 / telephone-event |
| RTP for SIP | UDP 1024–50000 from the Sipflex network address |
| Secure media | SRTP where deliberately enabled and supported on both sides |
Firewall guidance
Where an allow-list is required, permit only the protocols and ports used by your selected connection. Avoid opening a broad public SIP service when a registered outbound connection or restricted peer will work.
- Resolve Sipflex hostnames using DNS
- Permit established return traffic
- Allow the negotiated RTP path
- Do not rewrite SIP using an ALG
- Restrict public peering to expected sources
- Keep local PBX management interfaces private
TLS and SRTP
TLS encrypts SIP signalling and uses port 5061. SRTP protects the audio stream and is configured separately. Enabling only one side, or requiring encryption where the remote platform is not configured for it, can prevent calls from connecting or producing media.
Account-specific values override examples
Use the username, password and profile information displayed in your Sipflex portal. Never copy another customer’s credentials or substitute the portal password for the trunk password.