SIP Trunking icon

SIP Trunking

Protect your existing investment or refresh your telephony with Claranet

SIP Trunking connects your existing private branch exchange (PBX) to the national public switched telephone network (PSTN) using an IP connection. This provides a more flexible and low cost replacement to ISDN connections into the PBX. Alternatively, if you are looking to refresh your telephone system, see our Hosted Voice services.

Why choose Claranet as your SIP trunk service provider?

  • SIP trunk expert advice included
  • UK support 24x7x365 included
  • Get the most from existing hardware
  • Consolidate suppliers and save time and cost

SIP Trunking business benefits

Reduce costs

Reduce costs

By cutting your existing call plan and lines with our competitive rates and consolidating your telephony and data infrastructure

More functionality

More functionality

Get more out of your existing telephony hardware

Enhance resilience

Enhance resilience

Built-in business continuity options

Flexible and low cost replacement for ISDN lines

diagram for sip trunking process

SIP Trunking overview

  • Private IP telephony service that doesn’t touch the public internet
  • Geographic numbers
  • Flex the number of channels as your requirements change
  • Foundations of a future-proof communications solution
  • Stability and confidence through market leading partnership
  • 24x7x365 UK support
  • 99.987% service availability

How we work with you


Our experts can advise you how our telephony options can be tailored to your business needs


Working with Claranet removes the burden of project managing and carrying out the installation of your SIP Trunking service yourself, saving you time.


We take care of the ongoing 24x7 management of your service. However, you retain the control you need with access to around the clock UK support.


We work with you to ensure your service continually meets your needs.


  • Can I keep my existing PBX?

    Yes, provided it is one that is on our approved pre-tested list. Older PBXs may need an additional piece of equipment (either a SBC or gateway) to connect to the SIP trunking service. It may also be necessary to upgrade your PBX to the most recent firmware version.

  • What infrastructure do I need in place?

    A Claranet MPLS connection capable of carrying the voice channels required for your PBX. Additional hardware may be required.

  • Can I pair this with an existing solution?

    Yes, it is possible to mix SIP trunking from Claranet with traditional ISDN connectivity for resilience purposes.