How do You Implement SIP Trunking: Porting Numbers & Changing Networks

This is our 11th of 12 blogs on the subject of SIP Trunks. In this installment we will be taking a look at a variety of elements, including porting your numbers and changing networks. Subscribe in the box to the right to receive an email notification for each one in the series.

Local Number Porting (LNP)

Most customers wish to retain some or all of their telephone numbers as they move to SIP Trunking implementation. This process is called “porting.” Your new provider contacts the old provider and they work with a neutral third party (NPAC) to coordinate the change. 

Telephone Numbers

You must submit all of the telephone numbers you wish to port to your new carrier. You will only want to port numbers that are published. Unused DID’s or numbers that are part of a hunt group do not need to be ported. Remember, you are paying for every number you port.

Lead Time 

Converting from your old analog or PRI to SIP Trunking is a process that takes from 10 days to two months. Moving a few quantities that are on one phone bill is relatively fast. Moving numbers from multiple phone bills or larger numbers of numbers stretches out the time required. Lastly, some losing carriers have put roadblocks in place to purposefully slow the process down, thus keeping the revenue coming in for a bit longer.

Fax, Alarm & Point-of-Sale

If you want to completely rid yourself of your old telephone company you’ll need to convert these devices to an alternative method of connection, preferably Internet-based. Most people find it quite rewarding to be free of old their telephone company.

Letter of Agency

You will need to sign a carrier letter of agency that authorizes your new carrier to act on your behalf and place the necessary LNP order.

Copy of Your Phone Bill

You will be asked to provide a copy of your current telephone bill(s) to your new carrier. That bill can be no more than 30 days old.

PBX Preparation

On legacy PBXes, a gateway will need to be installed and tested in advance. For IP-based system, the requirements vary – some will require a card, others an external device called a Session Border Controller (BGP) and some a simple SIP Trunking license. For SIP-based PBXes such as the Digium Switchvox and Asterisk, no additional equipment or licensing is required. 

Data Network Changes

Your router and firewall must be voice-friendly, meaning that they’ll reliably pass phone traffic both directions. Depending upon your configuration, you or your data company may have to install a new router or firewall, set up QoS and define the proper routes for voice and data traffic. If you are going to change circuits, add a new circuit dedicated to SIP Trunking or setup a redundant network, you’ll have some technical work to do to establish this new cloud-friendly, VoIP capable network.

New Data Circuit (Optional)

You may need to order a new data circuit as per your SIP Trunking provider’s recommendations. The lead time for data circuits ranges from 10 business days (DSL) to several months (fiber). After the data circuit is delivered, it must be tested. Finally, you data vendor or IT person may have to make some internal network changes.

Porting Process

The actual porting of phone numbers on the due date is a delightfully quick and smooth process.

Canceling Your Old Telephone Service

While porting numbers to the new carrier, many circuits are automatically disconnected. However, most companies don’t port all of their numbers over. Make sure you contact your old phone company immediately after the port to confirm that they have or will disconnect all of the unused circuits.


Your business communications are now in the 21st century.

In our next and final blog of the series, we will discuss why choosing the right SIP Trunk Supplier is so important and what factors to consider when looking at providers. Make the best decision for your organization by getting all the facts!

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