Our SIP Trunk services allow you to connect your phone system to the public phone network via IP data services rather than traditional fixed line telephone services such as ISDN and PSTN. This can provide big benefits in terms of scalability and functionality, and often at dramatically reduced cost.

SIP connectivity is now standard on most modern phone systems and available as an simple upgrade to legacy systems so you can maintain your investment in your existing system and still benefit from the flexibility and big cost savings of SIP services.
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Reduce Cost

SIP Trunk services are less expensive per channel than ISDN and PSTN services. Cerberus SIP includes free UK landline calling (subject to AUP) and other call charges over our SIP Trunk services are very competitive and almost always significantly lower than comparable fixed line call tariffs. And if you have multiple sites with SIP Trunk services from us, calls between those sites will be free.


With SIP Trunk services it could not be easier to scale your connectivity. Provisioning additional SIP Trunks for additional outbound and inbound calls incurs minimal additional set-up charges and lead times. We aim to have your additional channels available within 4 working hours. And if you need additional numbers, again, we aim to turn your order around within 4 hours, then all you have to do is configure your equipment to handle the numbers and you are done. Individual SIP endpoint connections can scale from 1 to multiple channels as per your requirement.

Business Continuity and Reliability

With our SIP Trunk services, should your site experience an outage we can quickly redirect your calls to mobiles or to another site allowing you to carry on business until your site is back on line. And to maximise the reliability of your service, we can provide multiple servers on our network for your phone system to connect to as well as supporting inbound routing of calls to multiple endpoints on your system to support high-availability features in enterprise PBX systems such as Microsoft Skype for Business.

Number Flexibility

Our SIP Trunk services allow you to use any geographical numbers from anywhere in the country as well as to port in your existing geographical UK phone numbers, from one or multiple sets of lines, wherever they are located. We can also compliment all our fixed line and IP services with International inbound call routing to provide your organisation with a global presence.