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Setting up a SIP Trunk

Are you ready to install SIP trunking into your business’ phone system, but not sure how to do it? Read our guide to help you get started

SIP trunking is a virtual installation on a phone system that replaces the need for physical phone lines, as calls are made and received as data sent across an internet connection. It offers many benefits, including increased space and lower maintenance, as well as cost-savings and quicker disaster recovery options.

We’ll provide the key information you need to know about the available options for setting up a SIP trunk, including the factors to consider when deciding which installation method may be best for your business. Then, we’ll offer a step-by-step guide so you can do it yourself (providing you have the relevant skills and experience).

In this article, we’ll cover:

  1. How to set up a SIP trunk
  2. How to decide on an installation method


We’ll be diving straight into setting up a SIP trunk in this article.

If you need to find a provider, read our guide to the best SIP trunking providers for more information. Or, to help you work out a budget, check out our page on SIP trunking pricing.

Alternatively, if you’re ready to compare quotes for telephone systems now, fill in the form at the top of the page.


1. How to set up a SIP trunk


Essentially, there are three options available when it comes to setting up a SIP trunk. These are:

  • Use the SIP trunking provider
  • Hire a freelance IT specialist or an IT outsourcing company
  • Do it yourself


Use the SIP trunking provider

It may be possible to get assistance from your SIP trunking provider. The level of customer support and technical assistance available is a key factor to consider to ensure you pick a provider that’s right for your business.

While each provider may offer a different level of support and assistance, it should be possible to contact them with your queries, whether support is provided via phone, email or live chat. Alternatively, some providers may have online guides or forums where you can get help.

Hire a freelance IT specialist or an IT outsourcing company

With this option, you can hire a professional IT specialist or manager on a freelance basis to complete the task for you. Similarly, an IT outsourcing company could also be an option, depending on your business’ requirements and how many SIP trunks you need to have installed.

There will be costs to hire a professional for setting up a SIP trunk. This could be on a per hour, per day or ongoing basis, for example. However, you should consider the expense against how quickly and efficiently SIP trunking could be implemented into your phone system.

Do it yourself

Setting up a SIP trunk yourself is possible, although it may be somewhat of a challenge. You’ll need to have a fairly good grasp of IT management and coding skills, so this is perhaps more suitable for those that have worked in IT or software development.

You’ll need:

  • A computer with internet connection
  • Your PBX, SIP trunk and VoIP phone system account details
  • Your IP address
  • A gateway (to connect a non-IP phone system, if applicable)

Here is a step-by-step guide to the general process of setting up a SIP trunk. Note that each SIP provider may have steps that are specific to their product.

    1. Log into your PBX system


    1. Select the ‘trunks’ option


    1. Create and add a SIP trunk (this will connect the system externally)


    1. Name the trunk


    1. Set the outbound caller ID (your business’ phone number, or whichever number you want to use)


    1. Set the maximum number of channels


    1. Enter SIP peer details (this is how the systems talk to each other)


    1. Register the trunk (you may need to set up to register with the VoIP provider – this may be called a ‘register string’)


    1. Click ‘submit changes’


    1. Click ‘apply config’ (this is a key step as it makes the trunk live)


    1. At this stage, the trunk is set up and the PBX can connect to make and receive calls

Additionally, you can set the outbound and inbound routes after setting up a SIP trunk. These routes are how the PBX knows where to send the phone call, especially if it’s a system with multiple trunks, such as back-ups for the phone system.

    1. Check the registries or console commands for code


    1. Create an outbound route


    1. Name the outbound route


    1. Create dial patterns for phone numbers (this is based on the number of digits e.g. in the UK, both landlines and mobiles have 11 digits)


    1. Select the area code (e.g. +44; also 01, 02, 03)


    1. Select trunk


    1. Click ‘submit changes’


    1. Click ‘apply config’


    1. Create inbound route


    1. Determine the selection and name the route


    1. Select extensions


    1. Click ‘submit’


    1. Click ‘apply config’


    1. Test inbound and outbound calling – this can be done through an operator panel and by checking the call status


    1. Search to show peers – these should be pinging to show the gateways are working and/or the connection is live



What are peer details?

This involves setting up a registration with the SIP provider – the peer details set how the SIP trunk and IP system will talk to each other. You can create the code for how the systems will connect.

Note that there are many options for how to configure your phone system. The code you use will depend on your ability, as well as the level of functionality you need the system to have.


Some key points to remember are:

  • Ensure that you’re using a firewall, and an internet connection that can support SIP trunking sufficiently
  • Keep the IP address and SIP log-in details secure and private, as these can be used to access your phone system and server. It’s wise to set a strong password too
  • Check the server status – this is where any errors or issues will be raised, such as the status of the server or system
  • Only set up the SIP trunk account details once the server status is confirmed
  • Note that if there are any issues with the server or system status, these may come from your firewall, so be sure to check this
  • Remember to save changes along the way

2. How to decide on an installation method

There are a number of factors to consider when deciding which method will be best for installing SIP trunking into your business’ phone system. Have a think about the following questions to help you decide.

What is your skill level?

If you have some previous experience and knowledge of IT management, or coding ability, then you may be able to set up a SIP trunk independently.

However, using a professional (whether your provider or hiring a freelancer) is likely to be the best option for most start-ups.

When does it need to be ready?

Similarly, understanding how quickly you need to have SIP trunking installed and ready to use on your phone system will affect which method you use.

Doing it yourself (even for those with the necessary skills) will require you to set aside the time, taking you away from your other business duties. Decide if you can balance the time saved with the expense of hiring a professional.

How much is your budget?

Speaking of which, the amount you can afford to spend on SIP trunking is likely to be a key factor when making your selection. Setting up a SIP trunk yourself is technically free (although it will take you away from other work tasks, so bear that in mind).

However, hiring a professional will incur charges. You should also review what technical support and assistance your SIP trunking provider may be able to offer, and if there are any costs associated with this too.

Why are you using SIP trunking?

At this stage, it’s useful to think about why you’re installing SIP trunking. For example, if you run a start-up that needs one or two SIP trunks, your business’ needs are likely to be very different from a more established business that requires multiple trunks.

Likewise, specialist businesses that rely heavily on extensive phone systems (call centres, recruitment agencies, customer service companies, sales offices, PR companies or talent agencies, for example) would also have different requirements.

Therefore, the best installation method will depend on the reasons for choosing SIP trunking in the first place – whether you’re looking to cut call costs specifically, update your phone system in general, or provide more all-round cohesive communications.


Setting up a SIP trunk: A checklist

Here we outline some of the key points that need to be covered, whichever installation method you choose.

  • Do the number of SIP trunks cater for the number of phone system users?
  • Are the phones configured and set up?
  • Is there an appropriate amount (and strength) of bandwidth?
  • Are there disaster recovery plans in place?
  • Has the system been tested before going live?
  • Do existing phone numbers need to be transferred to the new system?
  • What security measures are protecting the system?


What are the next steps?

By now, you’ve learned more about how to choose the SIP trunking installation method that’s most suited to your start-up’s requirements, as well as how to do it yourself (if relevant).

Next, you can explore the rest of our channel on phones. Or, to get more specific information based on your business’ needs, simply complete the form at the top of the page to compare quotes for telephone systems now.

You can read more about SIP trunking by visiting our pages on:

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Scarlett Cook attends and reports on many industry events for, particularly those relating to communication, equality and diversity in entrepreneurship.

Since joining the team in 2018, she has developed our telephone systems and business mobiles topics as well as ‘how to’ guides, with her work having been referenced by brands such as Hiscox. Previously, she has written for audiences across the UK, Australia and New Zealand.