A SIP trunk for a call center has to accept dialer traffic, handle your peak channels and calls per second, deliver a caller ID people will answer, and bill in increments that suit short calls. For Vicidial, the trunk is added as a carrier with an account entry (the SIP connection) and a dialplan entry that matches the campaign's dial prefix.
What does a call center need from a SIP trunk?
Call center traffic is unlike office traffic: many calls at once, many short or unanswered attempts, and bursts when a campaign starts. Many routes refuse it or block it after a few hours. Before you buy, check each point below.
| Requirement | Why it matters |
|---|---|
| Accepts dialer traffic | Routes built for conversational traffic block predictive campaigns (see dialer traffic and VoIP routes) |
| Channels | Predictive dialers often need two to three lines per agent at peak |
| CPS | A campaign start can launch dozens of calls per second; above the limit you get 503s |
| CLI type | CLI or local CLI raises answer rates; use only numbers you have the right to present |
| Billing increment | 1/1 or 6/6 is far cheaper than 60/60 on short calls (see billing increments) |
| Short call rules | Some routes surcharge or cap calls under a few seconds |
| Codec | G.729 saves bandwidth with many agents; G.711 gives better audio and simpler setup |
Our guide on VoIP for call centers explains the route classes ("CC routes") that suppliers sell for this traffic.
How many channels and CPS does a call center need?
Start from agents and dialing mode. Manual and preview dialing need about one channel per agent on a call. Progressive dialing needs slightly more. Predictive dialing dials ahead of free agents, so peak channels are often two to three times the number of agents, depending on your answer rate. For CPS, take the number of calls the dialer launches in its busiest second, typically at campaign start or after a list reload, and add headroom. The sizing method is in SIP trunk channels and CPS.
How do you configure a SIP trunk in Vicidial?
Vicidial is an open-source contact center suite built on Asterisk. Trunks are managed in the admin interface under Admin, then Carriers.
- Add a new carrier and choose the server it runs on.
- Account entry: the SIP peer settings from your provider (host IP, port, codecs, and either IP authentication or username and secret). Most wholesale suppliers use IP authentication, so whitelist your server's public IP with them (see SIP peering vs registration).
- Registration string: only if the provider requires registration.
- Dialplan entry: a pattern that matches the dial prefix your campaigns use, strips that prefix and sends the number to the carrier in the format it expects (usually E.164, sometimes with a technical prefix).
- Campaign settings: set the campaign's dial prefix to match the carrier's dialplan entry, so each campaign uses the right trunk.
- Test with a few manual calls, check CLI, two-way audio and DTMF, then run a small campaign before scaling.
Behind NAT, set the external IP correctly and open the RTP port range, or you will hear one-way audio (see one-way audio fixes).
What does a SIP trunk for a call center cost?
Wholesale call center routes are priced per minute and per destination, sometimes with a monthly fee per channel. The real cost depends on the billing increment, your average call duration, the share of short calls and any surcharges. Compare offers with your own CDR profile, not only the headline rate (see VoIP termination rates).
Compliance comes with the trunk
The supplier does not make your campaigns legal; you do. Respect calling hours, consent and do-not-call rules in every country you call, and present only caller IDs you are entitled to use. In the US and Canada, calls also carry STIR/SHAKEN attestation, which affects whether your calls are labelled as spam. Abusive traffic gets routes cut off mid-campaign.
Getting call center SIP routes
Tell us your destinations, dialer, agents, channels, CPS, CLI type and target rate. VoIPMatcher sources a route that accepts that traffic from its carriers and manages it for you; your data is never shared or sold. See our VoIP termination service, then request a call center SIP trunk.
Frequently asked questions
What is the best VoIP provider for Vicidial?
There is no single best one. The right provider accepts your dialer type and destinations in writing, gives enough channels and CPS for your peak, delivers a CLI type that suits your campaigns, bills in short increments and supports IP authentication. Test two or three suppliers on the same campaign and compare ASR, ACD and cost per answered call.
Does Vicidial need a SIP trunk?
Yes, to call phone numbers outside your own system. Vicidial runs on Asterisk, and Asterisk reaches the telephone network through one or more carriers, which are SIP trunks in almost all modern setups. Older installations used E1 or T1 cards, but SIP trunks are now the standard choice.
Why does my SIP provider block dialer traffic?
Dialer traffic has many short and unanswered calls, high calls per second and a higher risk of complaints. Routes built for normal conversation cannot handle that profile, and downstream carriers may penalise the supplier for it. Declare your dialer and campaign type up front and buy a route that accepts it.
Can I use several SIP trunks in Vicidial?
Yes. You can add several carriers, each with its own dialplan entry and dial prefix, and assign different prefixes to different campaigns. This lets you send each destination to the best route, keep a backup route ready and compare suppliers side by side on real traffic.
Need a route?
Send the destination, route type and target rate. We reply with what we can deliver.