FCC LICENSED CARRIER ·499 FILER ·STIR/SHAKEN CERTIFIED
SIPNEX
Services · SIP Trunking for PBX

The carrier under your PBX.

Your PBX already does the routing, the extensions, the voicemail. What it needs from us is carriage: PBX SIP trunking direct from an FCC-licensed carrier — no channel caps, A-level attestation signed with our own STIR/SHAKEN certificate, and configuration guides for the platform you actually run.

Connect Your PBX → See Pricing
The trunk layer

Every PBX has two layers. We are the second one.

The software layer is the PBX you chose — 3CX, FreePBX, Yeastar, Avaya, or a dialer built on Asterisk. The carriage layer is the trunk underneath it: the connection that originates and terminates your calls on the public network, owns the numbers, and cryptographically signs every outbound call. SIP trunking for an IP PBX replaces the copper and PRI circuits that layer used to require with a connection your PBX registers to in minutes.

Splitting the layers is the point. Pick the PBX on features; pick the carrier on rates, attestation, and support. When either stops earning its keep, you swap it without touching the other — your numbers port, your trunk config moves, and your extensions never know. Running a dialer instead of an office PBX? That workload has its own page: dialer-grade SIP trunking.

Connect your PBX

Configuration guides for the platform you run.

SIP is a standard, and SIPNEX trunks speak it plainly: registration or IP authentication, G.711u primary, RFC 2833 DTMF. These guides map those settings onto each platform's own interface.

3CX

V20 custom trunk configuration

FreePBX

Web GUI trunk setup, tested templates

Asterisk

sip.conf / pjsip walkthrough

Yeastar

P-Series VoIP trunk configuration

FusionPBX

FreeSWITCH gateway setup

Avaya IP Office

SIP Line configuration

VICIdial

Dialer-grade carrier config

MicroSIP

Softphone directly on the trunk

UniFi Talk

What third-party SIP looks like
Why carrier-direct

What changes when the trunk comes from the carrier.

AT THE TRUNK LAYER SIPNEX (CARRIER) PLATFORM-BUNDLED MINUTES
Who signs your calls Us — own SP certificate, A-level Whoever sits upstream, often B-level
Concurrent channels Unlimited Per-seat or per-trunk caps
Per-minute rate control Published carrier rates Bundled into platform pricing
Number ownership & porting Yours, portable anytime Tied to the platform relationship
PBX platform choice Any SIP-capable system The platform's own
Support depth Engineers who read SIP traces Platform tier-1
Frequently asked

About PBX SIP trunking with SIPNEX.

What is PBX SIP trunking?
PBX SIP trunking is the carrier connection that gives your phone system access to the public telephone network over IP. The PBX handles everything inside your walls — extensions, voicemail, call routing — and the SIP trunk carries calls between your PBX and the outside world. One trunk replaces the analog or PRI lines a PBX historically needed.
What is a PBX trunk?
A trunk is the shared pathway between your PBX and the telephone network — historically a bundle of copper lines or a PRI circuit, today a SIP connection. Unlike an extension, which serves one user, a trunk carries many simultaneous calls. On a SIP trunk from SIPNEX there is no artificial channel cap: your concurrent-call capacity is set by your bandwidth and server, not by us.
Which PBX platforms work with SIPNEX trunks?
Any SIP-capable system: 3CX, FreePBX, Asterisk, FusionPBX, Yeastar, Avaya IP Office, Grandstream, VICIdial, and cloud platforms via BYOC. SIP trunking is a standard — if your PBX speaks SIP, it connects. We publish tested configuration guides for the common platforms and our engineers assist with the rest.
Do you support registration and IP-based authentication?
Both. Digest registration (username/password) is the simplest for PBXes behind dynamic IPs; IP authentication suits static-IP deployments and high-volume systems. Codec defaults are G.711u primary with G.729 available, and DTMF is RFC 2833 — the settings virtually every PBX expects.
Can I keep my phone numbers when I switch trunks?
Yes. Local and toll-free numbers port to SIPNEX while your current service stays live, and your PBX cutover is a configuration change, not a number change. Most operators run the new trunk in parallel, test outbound and inbound, then move routes over.
Does a hosted or cloud PBX still need a SIP trunk?
Yes — every PBX needs carriage; the only question is whether you choose the carrier or the platform bundles one invisibly. Choosing your own carrier (BYOC) means you control rates, attestation, and portability. If you'd rather we run the PBX layer too, that's our hosted PBX service.
Why does the carrier matter for caller ID reputation?
Because the carrier that puts your call on the PSTN signs it under STIR/SHAKEN, and the attestation level follows that carrier's relationship with you and your numbers. SIPNEX signs with our own SP certificate at A-level — the strongest signal that your PBX's outbound calls are legitimate. Trunks resold through intermediaries typically inherit B-level.

Related Guides

More Services

SIP TrunkingDID NumbersToll-FreeSMS MessagingCall TrackingHosted PBX

Point your PBX at a real carrier.

Tell us the platform and the call volume. You get trunk credentials within one business day, a configuration guide for your PBX, and an engineer on the line if the registration doesn't come up clean.

Connect Your PBX → Prefer We Run the PBX Too?
Or call direct: (833) 665-2220