SIP trunking
SIP trunks that keep your phones working through anything
Replace legacy lines or add resilient capacity to your PBX, UCaaS or contact center platform. Geo-redundant signalling, encrypted transport, channel limits you control and inbound numbers on the same account.
Your rate deck is available in the portal after sign-up.
SIP trunk · inbound + outbound
+1 416 ••• ••••
58%
4.6min
1.7s
Sample values · live per destination in portal
What it is
A SIP trunk is a virtual phone line between your system and the network
SIP (Session Initiation Protocol) is the standard that IP phone systems use to set up calls. A SIP trunk connects your PBX, UCaaS platform or contact center software to the public telephone network over the internet or a private link — replacing physical lines with capacity you can scale in software.
One trunk can carry many simultaneous calls ("channels"), inbound and outbound. Inbound calls arrive on DIDs (phone numbers) assigned to the trunk; outbound calls leave with a caller ID you are authorised to present. Because everything is software, you can add channels, move numbers between sites or fail over to a second data center without touching wiring.
CLIRoutes SIP trunks are built for availability. Signalling is served from geo-redundant edges, your trunk can register to or accept traffic from multiple endpoints, and inbound calls follow failover rules you define if your primary system is unreachable.
For businesses, that means phones that keep working when an office loses connectivity. For platforms, it means a carrier layer you can build tenants on without becoming a telecom operator yourself.
Inbound and outbound
One trunk handles both directions, with DIDs and caller IDs managed in the portal.
Encrypted by default
TLS signalling and SRTP media available on every trunk, with IP or credential authentication.
Geo-redundant edges
Signalling from multiple points of presence with automatic failover.
Channels you control
Set concurrency limits per trunk to cap spend and protect against abuse.
Who it’s for
For teams that need dependable voice connectivity
SIP trunking is the foundation layer under almost every modern phone system.
- 01
Businesses on IP PBX
3CX, FreePBX and Asterisk deployments replacing ISDN or analogue lines.
- 02
UCaaS providers
Carrier connectivity for multi-tenant platforms, with per-tenant numbers and limits.
- 03
Contact center platforms
Inbound queues and outbound agent calling on the same resilient trunks.
- 04
Multi-site organisations
Shared numbers and capacity across offices with central failover rules.
How it works
How a SIP trunk carries your calls
Two directions, one trunk. Redundancy at the edge means a single failure never takes your phones down.
- Hop 1Your PBX or platformRegisters or sends traffic from whitelisted IPs, over UDP, TCP or TLS.
- Hop 2CLIRoutes edgeGeo-redundant SIP edges authenticate, enforce channel limits and route calls.
- Hop 3Carrier networkOutbound calls terminate on quality tiers; inbound arrives from number-hosting carriers.
- Hop 4Caller or calleeInbound callers reach your DIDs; outbound recipients see your authorised CLI.
Inbound failover
If your primary system is unreachable, inbound calls follow your rules: secondary site, mobile number or voicemail.
Encrypted transport
TLS protects signalling and SRTP protects audio between your system and our edge.
Abuse protection
Channel caps, destination restrictions and spend alerts prevent toll fraud if a PBX is compromised.
Features
What you get with SIP Trunking
IP or credentials auth
Authenticate by whitelisted IP, SIP registration or both. Credentials rotate in the portal.
TLS and SRTP
Encrypted signalling and media for compliance-sensitive industries and remote workers.
Geo-redundant signalling
Multiple points of presence with DNS SRV failover so trunks survive an edge outage.
Bring or buy numbers
Port your existing numbers or provision CLIRoutes DIDs directly onto the trunk.
Channel limits
Set concurrent call limits per trunk and per direction to control spend and capacity.
Outbound coverage
Outbound calls use the same A-Z and CLI tiers as our wholesale customers.
Quality metrics
The numbers that matter here
Trunk traffic is mostly person-to-person, so ACD and PDD are the clearest indicators of call experience.
52%
ASR Answer-Seizure Ratio
For business calling, ASR reflects how often colleagues and customers pick up — usually high and stable.
3.4min
ACD Average Call Duration
Long ACD is normal on trunks. A drop often points to audio problems causing early hang-ups.
2.1s
PDD Post-Dial Delay
Users notice delay before ringing. Low PDD makes the phone system feel instant.
97%
NER Network Effectiveness Ratio
Confirms your trunk and our network completed attempts, separating config issues from route issues.
Gauge values are illustrative. Live per-destination ASR, ACD, PDD and NER are in your portal.
Setup
From sign-up to first call
Most PBXs connect in a few minutes with the settings below.
- 1
Open an account
Business verification and a note on the system you are connecting.
- 2
Create a trunk
Choose IP or credential authentication, transport and channel limits.
- 3
Add numbers
Buy DIDs or start a port-in. Assign each number to the trunk and set failover rules.
- 4
Fund your wallet
Top up with USDT, BTC or ETH. Your rate deck is available in the portal after sign-up.
- 5
Configure your PBX
Enter the trunk settings, place a test call in each direction and go live.
[cliroutes-reg]type=registrationtransport=transport-tlsoutbound_auth=cliroutes-authserver_uri=sip:sip.example-carrier.net:5061client_uri=sip:[email protected] [cliroutes-auth]type=authauth_type=userpassusername=YOUR_SIP_USERpassword=YOUR_SIP_SECRET [cliroutes]type=endpointtransport=transport-tlsmedia_encryption=sdesoutbound_auth=cliroutes-authaors=cliroutesCompare
How this route compares
Most customers run two or three route types side by side. Use the one that matches each traffic profile — mixing them on one trunk is the most common cause of poor answer rates.
| Attribute | CLI | IVR | CC | A-Z | SIP trunk | DID |
|---|---|---|---|---|---|---|
| Primary job | Outbound with your caller ID intact | Automated, consented campaigns | Agent-handled dialer outbound | Broad wholesale coverage | PBX / UCaaS connectivity | Inbound and owned CLI |
| Caller ID | Guaranteed passthrough | Authorised CLI, delivered | Authorised CLI, delivered | Tier-dependent | Your DIDs or authorised | Number you own |
| Typical call length | Medium to long | Short (under 60s) | Medium | Any | Any | Inbound, any |
| CPS / concurrency | Moderate, steady | High, approved per campaign | High concurrency, bursty | Scales with volume | Channel limit you set | Per-number channels |
| Consent review | CLI authorisation | Required per campaign | AUP + DNC hygiene | AUP | AUP | Regulatory documents |
| Typical buyers | Sales teams, BPOs | Notification & survey platforms | Call centers, dialer operators | Resellers, carriers | Businesses, UCaaS | Support desks, local presence |
- CLI
- Primary job
- Outbound with your caller ID intact
- Caller ID
- Guaranteed passthrough
- Typical call length
- Medium to long
- CPS / concurrency
- Moderate, steady
- Consent review
- CLI authorisation
- Typical buyers
- Sales teams, BPOs
- IVR
- Primary job
- Automated, consented campaigns
- Caller ID
- Authorised CLI, delivered
- Typical call length
- Short (under 60s)
- CPS / concurrency
- High, approved per campaign
- Consent review
- Required per campaign
- Typical buyers
- Notification & survey platforms
- CC
- Primary job
- Agent-handled dialer outbound
- Caller ID
- Authorised CLI, delivered
- Typical call length
- Medium
- CPS / concurrency
- High concurrency, bursty
- Consent review
- AUP + DNC hygiene
- Typical buyers
- Call centers, dialer operators
- A-Z
- Primary job
- Broad wholesale coverage
- Caller ID
- Tier-dependent
- Typical call length
- Any
- CPS / concurrency
- Scales with volume
- Consent review
- AUP
- Typical buyers
- Resellers, carriers
- SIP trunk
- Primary job
- PBX / UCaaS connectivity
- Caller ID
- Your DIDs or authorised
- Typical call length
- Any
- CPS / concurrency
- Channel limit you set
- Consent review
- AUP
- Typical buyers
- Businesses, UCaaS
- DID
- Primary job
- Inbound and owned CLI
- Caller ID
- Number you own
- Typical call length
- Inbound, any
- CPS / concurrency
- Per-number channels
- Consent review
- Regulatory documents
- Typical buyers
- Support desks, local presence
Compliance notes
Rules that keep this route stable
Trunks carry emergency, inbound and outbound traffic. A few rules keep that safe and lawful.
Emergency calling
Emergency service availability varies by country and number type. Check the country page and configure local emergency routing where required.
Authorised caller ID
Outbound calls must present numbers assigned to the trunk or that you are authorised to use, attested correctly in the US and Canada.
Secure your PBX
Use strong credentials, restrict international destinations you do not need and set channel caps.
Number regulations
Some countries require proof of local address or business registration for numbers. We collect documents in the portal.
Coverage
SIP Trunking by country
Outbound coverage in 100+ countries and inbound numbers in many of them. See country pages for availability.
- United States
- United Kingdom
- Canada
- Australia
- Germany
- France
- Spain
- Italy
- Netherlands
- Belgium
- Switzerland
- Austria
- Sweden
- Japan
- Brazil
- Mexico
Why redundancy matters more than features
Phone systems are judged on the days they fail. A trunk that offers every feature but goes down with a single data center leaves your customers on hold indefinitely. CLIRoutes trunks are designed so that no single component — edge, carrier or your own primary site — takes your phones offline.
Pair trunks with CLIRoutes DIDs for one account covering inbound numbers, outbound routes, CDRs and quality data. Your rate deck is available in the portal after sign-up.
FAQ
SIP Trunking FAQ
Can’t find what you need? Our routing team answers within the hour, around the clock.
What is SIP trunking?
SIP trunking connects an IP phone system to the public telephone network over the internet, replacing physical phone lines. Each trunk can carry many simultaneous calls in both directions.
Which PBX systems are supported?
Any standards-compliant SIP system. We publish guides for 3CX, FreePBX, Asterisk and FreeSWITCH, and our NOC can help with others.
Can I keep my existing numbers?
In most countries, yes. Start a port-in from the portal; we guide you through the documents and schedule the cutover.
Do you support encryption?
Yes. TLS for signalling and SRTP for media are available on every trunk at no extra configuration complexity.
What happens if my PBX goes offline?
Inbound calls follow your failover rules — for example, to a secondary SIP endpoint, a mobile number or voicemail — until your primary system is back.
How many channels can a trunk have?
You set the limit. Channels are not sold in fixed bundles; you control concurrency per trunk to match your needs and budget.
Do your trunks support emergency calling?
Emergency calling depends on country and number type. Country pages explain availability, and you should configure local emergency routing where required by law.
Can I use SIP trunks for a contact center?
Yes. Many contact centers use trunks for inbound queues and agent outbound. For heavy predictive dialling, add CC routes for that traffic.
Trunks that stay up when it counts
Open an account, create a trunk and place your first call in minutes. Your rate deck is available in the portal after sign-up.