VoIP carrier insights.
The SIPNEX blog: practical guides to SIP trunking, STIR/SHAKEN, dialer compliance, and caller ID reputation for teams running outbound and inbound voice.
What is SIPNEX VoIP?
SIPNEX is an FCC-licensed VoIP carrier providing SIP trunking for high-volume outbound operations, including VICIdial and other predictive dialers. SIPNEX holds its own STIR/SHAKEN service-provider certificate, files FCC Form 499, and is registered in the Robocall Mitigation Database. Customer calls are signed directly with A-level attestation.
Business Phone Number Registration: Every Portal
Every business phone number registration portal — Free Caller Registry, First Orion, Hiya, Verizon — by who may use which, and what none of them can fix.
STIR/SHAKEN on Asterisk and FreePBX
What Asterisk’s res_stir_shaken module actually does, why self-signing needs an SP certificate most PBX shops can’t get, and the carrier path that works.
Choosing a SIP Trunk for VICIdial: 7 Criteria
A criteria-first scorecard for choosing a VICIdial SIP trunk: written dialer policies, CPS headroom, billing increments, attestation, and suspension red flags.
Caller ID Test: See What Your Calls Display
How to run a caller ID test: place calls to phones on each major carrier, record the displayed name, number, and spam label — and how to re-test at scale.
Dialer Account Suspended? What to Do Today
Dialer account suspended mid-campaign? The export checklist to run today, why providers shut off dialer traffic, your number-porting rights, and the trunk cutover.
SIP 403 Forbidden: Causes and Fixes
SIP 403 Forbidden means the carrier understood your call and refused it. The five causes operators actually hit, how to tell them apart, and the fix for each.
SIP 503: Service Unavailable, Explained
SIP 503 Service Unavailable explained: what RFC 3261 says, the carrier causes dialer operators actually hit, the Asterisk AUTO-CONGEST mixup, and the fixes.
SIP Providers That Allow Auto Dialers
The published allow/ban policies of Twilio, Telnyx, voip.ms, RingCentral, and 8x8 on auto dialer traffic — and what dialer-friendly carriers ask for.
VICIdial Backup Carrier & Failover Setup
How to add a backup carrier in VICIdial: the second carrier entry, dial-prefix routing per campaign, failover on 503s, and A/B testing connect rates.
VICIdial Troubleshooting: Symptom-First Guide
VICIdial troubleshooting by symptom: dropped calls, dead air, empty hopper, one-way audio, spam flags — which layer owns each fault and where the fix lives.
TCPA Text Message Rules: Consent That Holds Up
TCPA rules for text messages: consent tiers, the 2025 revocation rules, quiet hours, record-keeping, and a send-day texting checklist.
Campaign Verify: Political SMS Vetting Explained
What Campaign Verify is, who needs a token, how political 10DLC vetting works, and why unverified political texting risks blocking in the 2026 cycle.
DTMF on SIP Trunks: RFC 4733 and Dead IVR Digits
How DTMF digits cross a SIP trunk — inband, RFC 4733 telephone-event, or SIP INFO — why IVR digits vanish, and a packet-capture checklist to fix them.
How to Fix Packet Loss on VoIP Calls
How to fix packet loss on VoIP calls: map choppy audio to a direction, localize the loss with mtr and RTCP, then apply fixes ranked from QoS to SQM.
Local Presence Dialing: Legit Setup vs Spoofing
Local presence dialing done right: owned local DIDs, A-level attestation, callback routing — and where the line falls against neighbor spoofing.
SIP Code 603 Declined — Now 'Network Blocked'
SIP code 603 explained: the RFC 3261 Decline meaning, the FCC 603+ Network Blocked standard effective March 25, 2026, and how operators fix blocked calls.
SIP Response Codes: The Operator's Reference
SIP response codes in one operator reference: all six classes, the codes you actually see on trunks, common causes, and which failures are safe to retry.
What Is SIP ALG and Why You Should Disable It
SIP ALG rewrites SIP headers as calls cross your router — causing one-way audio, 32-second drops, and dropped registrations. How to find and disable it.
Bring Your Own Carrier (BYOC): How It Works
Bring your own carrier (BYOC) from the carrier side: how it works with Twilio, Zoom, Teams and Genesys, why operators do it, and when to skip it.
Least Cost Routing in Telecom: How LCR Works
What least cost routing means in telecom, how LCR engines rank rate decks and fail over between routes, and why the cheapest route is often the worst one.
Potential Spam: How to Fix the Label on Your Calls
Why business calls get labeled Potential Spam, Spam Risk, or Scam Likely, and the step-by-step remediation playbook that actually clears the labels.
What Is an LRN? Location Routing Numbers Explained
What an LRN (Location Routing Number) is, how LRN dips work in the call path, and why termination billing follows the LRN instead of the dialed number.
A-Level vs B-Level STIR/SHAKEN Attestation
What A, B, and C STIR/SHAKEN attestation levels mean, who sets them, how terminating networks use them, and how to check the level your calls carry.
A2P 10DLC Registration, Step by Step
A2P 10DLC registration step by step: brand vetting, campaigns, fees, and throughput, plus what financial services and telecom senders need to watch.
FCC Abandoned Call Rate: The 3% Rule Explained
The FCC’s 3% abandoned call rule for telemarketing calls: how it is measured, what every abandoned call must play, and how to keep a predictive dialer under the cap.
Call Center Compliance: Federal & State Rules
Call center compliance explained for dialer operators. TCPA, TSR, state telemarketing laws, STIR/SHAKEN, DNC, and the carrier infrastructure that supports it.
Caller ID Spoofing: How It Works and the Law
Caller ID spoofing explained from the carrier side. How spoofing happens technically, the Truth in Caller ID Act, and STIR/SHAKEN’s role in fighting it.
CNAM Explained: What It Is & How CNAM Lookup Works
What CNAM is, how a CNAM lookup works, why caller ID shows the wrong name, and how branded calling and Rich Call Data are changing name display in 2026.
E.164 Format: International Phone Numbers
E.164 phone number format explained for VoIP operators. What it is, why SIP trunks require it, formatting rules, and common mistakes that break call routing.
Hosted PBX vs SIP Trunking: Which Is Right?
Hosted PBX vs SIP trunking explained by a carrier. When to let someone else run your phone system vs when to run your own with a direct trunk.
How Many SIP Trunks Do I Need? Sizing Guide
SIP trunk sizing explained by an FCC-licensed carrier. Concurrent channels, bandwidth math, VICIdial capacity planning, and why the question itself is outdated.
How STIR/SHAKEN Certificates and Signing Work
Inside the STIR/SHAKEN certificate chain: PASSporT tokens, JWT signing, SIP Identity headers and STI-GA/STI-PA/STI-CA, from a carrier that signs its own calls.
How to Get a Toll-Free Number
How to get a toll-free number for your business. The provisioning process, RespOrg system, number selection, porting, costs, and setup timeline.
Number Portability: How to Port Your Numbers
Number portability explained step by step: the LNP process, LOA and LSR requirements, FOC dates, port timelines, free porting, and porting to SIPNEX.
Predictive vs Progressive vs Preview Dialer
The three dialer modes compared for call center operators. When to use predictive, progressive, or preview dialing based on campaign type, compliance, and conversion goals.
7 Questions to Ask Your SIP Trunk Provider
Seven vetting questions for a SIP trunk provider — channel caps, whose certificate signs your calls, billing increments, fees — and what a weak answer sounds like.
FCC Robocall Mitigation Database Explained
The FCC Robocall Mitigation Database explained. What carriers must file, what happens to non-filers, and why your carrier's RMD status affects your calls.
SIP Trunk Configuration Guide: Asterisk & FreePBX
SIP trunk configuration walkthrough for Asterisk and FreePBX, plus the basics for any PBX: carrier credentials, codecs, NAT, DTMF, firewall rules, and testing.
SIP Trunk Pricing: What You Should Pay
SIP trunk pricing in plain terms: per-minute rates, per-channel fees, DID costs, billing increments, and how to compare quotes like for like.
TCPA Compliance Checklist for Dialer Operators
A TCPA compliance checklist for dialer operators: consent, ATDS rules, DNC, calling hours, abandon rates, and the 2025 revocation rules.
VICIdial SIP Trunk Setup: Complete Guide
Step-by-step VICIdial SIP trunk configuration for SIPNEX. sip.conf settings, codec recommendations, DTMF, NAT traversal, and troubleshooting common issues.
What Is a DID Number? Operator's Guide
DID numbers explained by an FCC-licensed carrier. What DIDs are, how they work, provisioning, porting, and why your DID strategy affects your answer rate.
What Is a Predictive Dialer? Operator's Guide
How predictive dialers pace calls, the FCC 3% abandonment cap, and what a dialer demands from its SIP trunk: channels, post-dial delay, attestation and codecs.
What Is SIP Trunking? How It Works, What It Costs
SIP trunking explained by an FCC-licensed carrier: what it is, how it works, what it costs, and why it replaced PRI and traditional phone lines for voice.
Frequently asked questions.
Can I run VICIdial on a SIPNEX SIP trunk?
Yes. SIPNEX is built for teams that run VICIdial and other predictive dialers. Trunks carry unlimited concurrent channels with no per-channel fees. No channel limit throttles your dialer's pacing algorithm.
Is SIPNEX the carrier of record or a reseller?
SIPNEX is the FCC-licensed carrier itself, not a reseller marking up an upstream provider's service. Calls are signed with SIPNEX's own STIR/SHAKEN service-provider certificate rather than passing through an upstream carrier's attestation.
What topics does the SIPNEX blog cover?
SIP trunk configuration, STIR/SHAKEN attestation levels, TCPA and FCC compliance, caller ID reputation, and predictive dialer operations. Every post is a practical guide: choosing a carrier, weighing a published rate against real-world call quality, or keeping outbound campaigns compliant.