Connect your phone system (SIP/PBX)

Connect Synthflow to your PBX or carrier via SIP trunking.

This guide is intended for system administrators and technical staff with experience configuring SIP trunks and PBX integrations. If you’re new to SIP trunking, consider starting with our simpler options like Twilio integration or buying a number directly.

Prerequisites

Public IP(s) or SBC hostname for signaling/media.
SIP credentials or IP‑ACLs.
Desired codecs and DTMF method.
Firewall rules to allow our SBC addresses and ports.
Enterprise account with custom number import access.

Note
We provide SIP endpoints and credentials in the Synthflow Console after you request access.

Typical trunk settings

Transport: UDP or TCP.
Codecs: G.711 μ‑law/A‑law. Opus.
DTMF: RFC 2833 (RTP events). SIP INFO.
Registration: Static trunk (IP‑based) or SIP REGISTER (digest auth).
NAT: Symmetric NAT supported with media pinholes and rport.

Tip
Start with G.711 for maximum compatibility across systems.

NAT and failover

Configure SIP timers and keep‑alives to maintain NAT bindings.
Provide multiple destination IPs or DNS SRV for failover when available.
Set reasonable retry intervals to avoid storming.

Integration matrix

Platform	SIP transport (UDP/TCP)	DTMF (RFC2833 / SIP INFO)	Registration (Static/REGISTER)	NAT traversal	Codecs (G.711 / Opus)
Asterisk	UDP, TCP	RFC2833, SIP INFO	Static, REGISTER	Yes	G.711; Opus
Cisco (CUCM/CUBE)	UDP, TCP	RFC2833	Static, REGISTER	Yes	G.711; Opus
Avaya	UDP, TCP	RFC2833	Static	Yes	G.711
Genesys	UDP, TCP	RFC2833	Static	Yes	G.711; Opus
Generic SIP trunk	UDP, TCP	RFC2833, SIP INFO	Static, REGISTER	Yes	G.711; Opus

Note
Some features depend on your specific version and configuration. Contact our team to confirm compatibility before production deployment.

Importing your numbers

Once you have configured your SIP trunk or PBX integration with the settings above, you need to import your phone numbers into Synthflow so we can route calls correctly.

The import process is done through the Synthflow portal and requires you to specify:

Your phone number in E.164 format
SIP domain and authentication credentials
Outbound proxy settings (if using non‑standard ports or mid‑registrar)

For detailed step‑by‑step instructions and field‑level explanations, see Custom phone numbers.

Tip
Have your SIP credentials, domain, and trunk configuration details ready before starting the import process.