VoIP

The Complete VoIP Troubleshooting Guide: Symptom → Cause → Fix

Bookmark this one. Organized by symptom, here's the field guide our techs carry in their heads — the most common VoIP problems, their usual causes, and what actually fixes them.

Choppy, robotic, or garbled audio

Usual cause: network congestion — voice packets stuck behind bulk traffic. Fix: QoS on the router prioritizing voice; check for saturating uploads (cloud backups love business hours); verify jitter and packet loss with a line test. Persistent garble on one phone points to its cable or port.

One-way audio (they hear you, you don't hear them — or reverse)

Usual cause: firewall/NAT misbehavior, with SIP ALG the notorious repeat offender. Fix: disable SIP ALG on the router; verify the firewall isn't mangling media ports. This one is configuration, not carrier — almost every time.

Dropped calls at consistent intervals (e.g., exactly 15 minutes)

Usual cause: session timers or NAT table expiry — the network “forgets” the call midstream. Fix: registration/keepalive settings and router session timeouts; again SIP ALG earns suspicion.

Phones not registering / “No Service”

Usual cause chain: internet down → DNS issues → firewall blocking → provisioning misconfig. Fix: confirm internet, reboot phone and check registration status, verify nothing upstream changed (new router or ISP equipment is the classic silent culprit).

Echo

Usual cause: acoustic — speakerphone volume, cheap headsets — more often than network. Fix: lower speaker volume, swap the headset, test the handset; persistent echo across devices merits a carrier/line look.

Caller ID showing wrong or “Spam Likely”

Fix: outbound CNAM registration with your provider, and number reputation registration (free carrier registries) — a setup item most installs skip. Ask us; it's quick.

When the checklist doesn't crack it

Intermittent, multi-symptom, or “it's been flaky since the office moved” problems usually trace to infrastructure — cabling, switches, or design. That's a measurement visit, not more rebooting: our techs test lines, certify runs, and fix the actual cause. One service call typically ends months of tolerated weirdness.