Wholesale: Products & Services

Access To Telephone Numbers - V12

History Log

Product Description

The North American Numbering Plan, or "NANP," refers to the telephone numbering scheme used for the public switched telecommunications networks to route calls to subscribers. The NANP format is a 10-digit number that consists of a 3-digit NPA code (commonly referred to as the area code), followed by a 3-digit NXX code (also referred to as the Central Office (CO) code) and a 4-digit line number.

The Telecommunications Act of 1996 directed the Federal Communications Commission (FCC) to "designate an impartial numbering administrator to make telecommunications numbering available on an equitable basis." The FCC directed the North American Numbering Council (NANC) to recommend a neutral party to serve as the North American Numbering Plan Administrator (NANPA), known as the "Code Administrator," to accomplish this task. Lockheed Martin IMS was selected as the new NANPA. Lockheed Martin IMS became NeuStar™, a separate company, on Dec. 1, 1999. Additional information on numbering resources and assignments administered by NANPA, includes Area Codes (NPA), Carrier Identification Codes (CIC), N11 Codes, Service Access Codes, Vertical Service Codes, and NXX Codes, can be found on the NANPA web site.

Numbering information is included in the national Business Integrated Routing/Rating Database System (BIRRDS), previously known as the Routing Data Base System (RDBS) and the Business Rating Input Database System (BRIDS) and the Line Information Data Base (LIDB) Access Support System (LASS). The BIRRDS contains detailed descriptions of all Competitive Local Exchange Carriers (CLECs) and wireless companies networks in the NANP area necessary for message routing, common channel signaling call setup, operator service access routing and message rating. The LASS contains information necessary for credit card and calling card services. Numbering information included in these databases provides the industry with notifications of changes through the database outputs. Examples of the database outputs include the Local Exchange Routing Guide (LERG™), the NPA/NXX Activity Guide (NNAG), the Terminating Point Master (TPM™), the NPA/NXX Vertical and Horizontal Coordinates Data (VHCD) and the LIDB Access Routing Guide (LARG).

You are responsible for administering numbering resources assigned to you and for updating the national databases (BIRRDS, LASS), when appropriate. In addition, you are responsible for programming and updating your own switches and network systems, pursuant to the LERG, to recognize and route traffic to CenturyLink™'s NXX codes. You are also responsible for notifying your end-users of any changes in numbering or dialing arrangements, such as the introduction of a new NPA.

NXX Assignments and Activations
NXXs are assigned within geographic NPAs for use at a Switching Entity or Point of Interconnection (POI). NXX codes are normally associated with a specific geographic location within an NPA. Examples of uses for NXX codes include Plain Old Telephone Service (POTS), Centrex, Direct Inward Dialing (DID®), cellular mobile service, pagers, data lines, facsimile, coin phones and customer-owned pay phones.

When you request an NXX code from NANPA, you must comply with the Industry Numbering Committee (INC) Central Office Code Assignment Guidelines (COCAG). The COCAG is published by the INC as INC 95-0407-008, and can be obtained by accessing Alliance for Telecommunications Industry Solutions (ATIS), under INC documents. The latest version of the Guidelines is considered the current standard. While the Guidelines were developed at the direction of the FCC, they do not supersede applicable local, state, federal governmental or the NANP area governmental regulations relative to the services you wish to provide.

The COCAG will describe all the steps necessary for you to request a new NXX code. The Guidelines include the following activities:

  • Submitting your request to the appropriate Central Office Code Administrator using the NXX Assignment Request and Confirmation Form (Part 1 to NANPA).
  • You are responsible for providing the information shown in Part 2 of the NXX Assignment Request Form that includes routing information for entry into BIRRDS.
  • You are responsible for entering NXX information into the appropriate LASS, if you are planning to provide credit card or calling card services.
  • You are responsible to provide notification to the Central Office Code Administrator of any changes to the information (e.g., tandem homing arrangements, Operating Company Number (OCN), switching points, rate center and transfer of a code to a different company).
  • You are responsible for submitting Forecast and Utilization Reports to NANPA.
  • Any other criteria for the assignment of NXX Codes as specified in the COCAG.

CenturyLink NPA NXX Code Activation Process
When you request to have an NXX code activated within the CenturyLink territory, in addition to following the COCAG, you need to be familiar with the related CenturyLink NPA NXX Code Activation Process.

The CenturyLink NPA NXX Code Activation Process is based on the requirements identified in the COCAG. You must first input your new NXX code information into the BIRRDS, or have contracted with another party to provide the input on your behalf. The BIRRDS data includes information on NXX codes and current network configurations necessary before your CO code can become active. CenturyLink pulls the "All Pending Changes," or XAP report, from the BIRRDS on a daily basis and issues the routing order to activate the new NXX Code within the CenturyLink network. The routing information is obtained from the LERG and the trunk group routing information you provided to CenturyLink when you issued your trunk group orders.

In some instances, CenturyLink also recommends that you complete the CenturyLink NPA NXX Code Request Routing Form described in the Ordering Section of this guide when requesting code activations where you have more than one routing option available, or where unique routing specifications are required.

Number Pooling
Thousands-block Number Pooling is a process by which 10,000 numbers in a NXX are separated into 10 blocks of 1,000 numbers each (thousands-blocks), and allocated within a rate center by a neutral administrator. Number Pooling has been established in accordance with the FCC Report and Order No. 00-104 and the INC Thousands Block Pooling Administration Guidelines (INC 99-0127-023).

The term Pooling Administrator refers to the entity or entities responsible for administering a thousands-block number pool. The FCC selected NeuStar as the national Pooling Administrator. Where thousands-block Number Pooling has been implemented, the Pooling Administrator is authorized to allocate thousands-blocks to CLEC applicants and to apply for additional NXXs for pool replenishment. In areas where thousands-block Number Pooling has been implemented, the NXX code holders are designated as the "LERG Assignee". Where Number Pooling has not been implemented, CLEC providers that have been assigned NXXs are termed "code holders". CLECs obtaining blocks from the Pooling Administrator are termed "block holders." It is the responsibility of the block holder to know and comply with the INC Thousands Block Pooling Administration Guidelines. The Pooling Administrator will select a "LERG assignee" when codes need to be added to the pool, in accordance with the INC Guidelines. The LERG assignee will fill out the CO Code Request and submit it to the Pooling Administrator, who will forward the request to the Code Administrator. For more information on Number Pooling, refer to NeuStar. For a copy of the Pooling Administration Guidelines, refer to ATIS and click on INC documents.

CenturyLink Dialing Plans
Local Dialing Parity provides all CLECs with the ability to have nondiscriminatory access to telephone numbers, operator services, directory assistance, and directory listings, without unreasonable dialing delays. For more information regarding Local Dialing Parity and the CenturyLink dialing plans, refer to Local Dialing Parity.


There are no charges associated with the activation of NXX codes within the CenturyLink network.


Not applicable to this product.


Not applicable to this product.



If you are a new CLEC and are ready to do business with CenturyLink, view Getting Started for Facility-Based CLECs or Getting Started for Resellers. If you are an existing CLEC wishing to amend your Interconnection Agreement, you can find additional information in the Interconnection Agreement.


The following actions must be completed prior to the activation of an NXX code within the CenturyLink territory:

  • Your NXX Code was requested and input into the LERG in accordance with industry guidelines.

  • You have an approved Interconnection Agreement.

  • You have determined your method of Interconnection and have ensured Interconnection trunks and facilities are in place prior to activation of an NXX code.

  • You have reviewed the CenturyLink NPA NXX Code Activation process.


You do not need to order NPA NXX Code Activation within CenturyLink COs.

Your NXX(s) are activated in the CenturyLink network as a normal course of business in accordance with the information you provide in the LERG. However, there are times when the routing information required to activate a new NXX is not discernable from the information contained in the LERG. For example, this could happen when you have a single switch served by multiple trunk groups, or when you do not have trunk groups in place prior to the NXX activation date. CenturyLink will attempt to determine the proper routing based on the information contained in your Local Service Requests (LSRs), LERG, and from your existing trunking records. However, the proper route is not always discernable from the information available to CenturyLink. In these instances, the CenturyLink Routing Group will refer routing questions to the CenturyLink Service Delivery Coordinator (SDC). The SDC will further investigate the routing information and, when necessary, call you to resolve any issues. If the SDC is not able to obtain all the necessary information after the SDC has contacted you, the SDC may additionally request that you complete the NPA NXX Code Request Routing Form.

You may also want to initiate the NPA NXX Code Request Routing Form on a proactive basis, prior to being contacted by CenturyLink, to ensure accurate routing of your code in accordance with your specifications.

NPA NXX Code Request Routing Form (previously known as the NPA NXX Code Request Supplemental Form)
When the routing information is not discernable, as identified above, CenturyLink will initiate a request that you complete the NPA NXX Code Request Routing Form. The information contained on this form is necessary to route calls to your NXX code appropriately. For each NXX code assigned to you by the NANPA, you will need to provide CenturyLink with the Common Language® Location Identifier (CLLI™) of your CO switch serving the new NXX code, or your (POI), if it is located in a different LATA, and the CLLI code(s) of the CenturyLink tandem where traffic will be routed. For NXX codes assigned to existing Local Interconnect Service (LIS) trunk groups, you will need to provide CenturyLink with the assigned Trunk Group Serial Number (TGSN or Two-Six Code) for the NXX code that is to be activated.

If you are aware that you have multiple routing options available within the CenturyLink network at the time you complete the Part 2 BIRRDS input, completing the CenturyLink NPA NXX Code Request Routing Form at the same time will ensure that your NXX code is routed to your specifications.

If routing information is not available, and the CenturyLink NPA NXX Code Request Routing Form has not been received, the CenturyLink routing order is in jeopardy until the appropriate routing information is received. Complete and accurate information must be received by the CenturyLink routing group 25 days prior to the activation due date. CenturyLink NPA NXX Code Request Routing Form can be sent to:

CenturyLink Routing Group
Email: routing@centurylink.com Fax: 303-707-9578

Send a copy of your CenturyLink NPA NXX Code Request Routing Form to your CenturyLink Service Manager.

Provisioning and Installation

CenturyLink uses a designed services coordinated installation provisioning process to fulfill your LIS orders associated with the opening of new NXX codes. Refer to the Provisioning and Installation Overview for more detailed information regarding the provisioning of your service.

NXX Code Activation Intervals
Requests for code assignments cannot be made more than six months prior to the requested effective date. You must request an effective date for the NXX code activation at least 66 calendar days after your request is sent to NANPA. This 66-calendar day interval is derived by adding the 21 days allotted for code request processing to the industry standard of 45 days for code activation. NXX code activation begins from the date the NXX code request is input into RDBS and BRIDS. Download the Industry NXX Code Activation Timeline for more information. Note that Interconnection trunks and facilities must be in place prior to activation of an NXX code. Such arrangements are outside the scope of these interval guidelines.

NXX Code Testing
CenturyLink will perform testing for new NXX codes as a normal course of business when test numbers are provided. CenturyLink requests that you establish a four-digit test line number for use with each new NXX code that you open up. Test numbers associated with an NXX code should be published in the LERG and included in your NPA NXX Code Request Routing Form, if one is issued.

Maintenance and Repair

CenturyLink will work cooperatively with you to resolve trouble reports when a trouble condition has been isolated and determined to be within the CenturyLink network. The Account Maintenance Support Center (AMSC) is open 24 hours a day and can be reached at 1-800-784-3414.

NPA NXX Trouble Reporting
When calling CenturyLink to report trouble that may be related to a recent NXX Code Activation, you should complete the following activities prior to reporting the trouble:

  • Ensure that you have met all necessary Code Holder Responsibilities, as defined in the COCAG, and that your Interconnection trunks and facilities are in place prior to activation of a code. If you have not met the above requirements, you will need to make those arrangements and go back through the NANPA process to change the requested effective date of the new code.
  • Determine which service provider's network has originated the call (e.g., wireless or other Local Exchange Company (LEC) network), and contact that service provider to isolate the trouble.
  • If it is determined that the trouble involves the CenturyLink network, report the trouble to CenturyLink (be prepared to provide your trunk group routing information for the location where you are experiencing trouble).

Contact the AMSC to report the trouble. You may submit trouble reports via e-bonding or by utilizing your normal trouble reporting channel into the AMSC.

The following information should be provided to the CenturyLink Repair Service Attendant (RSA):

  • Trunk Group Serial Number (TGSN or Two-Six Code).
  • NPA NXX Code experiencing trouble.
  • NXX Code Holder Name (if other than you).
  • Originating and Terminating Telephone Numbers that are experiencing the trouble.
  • Description of the Problem. (Is this related to a new NXX Code Opening? When was the requested turn-up date? Provide any details to help with isolation of the trouble.)
  • Recording Trailer and Description (if available). The Recording Trailer is the message you receive when a code fails.

Escalation of Trouble Ticket and Status Requests:

Contact Toll- Free Number Information to Provide
CenturyLink AMSC Utilize your normal trouble reporting channel into the AMSC All details necessary to open the trouble ticket
Escalation of Trouble Ticket
Request CenturyLink Duty Supervisor or the Next Level of Supervision Utilize your normal trouble reporting channel into the AMSC
  • Trouble Report
  • Ticket Number
  • Billing

    Not applicable to this product.


    Local CenturyLink 101 "Doing Business With CenturyLink"

    • This introductory web-based training course is designed to teach the Local CLEC and Local Reseller how to do business with CenturyLink. It will provide a general overview of products and services, CenturyLink billing and support systems, processes for submitting service requests, reports, and web resource access information. Click here for Course detail and registration information.

    View additional CenturyLink courses in the Course Catalog.

    Industry training that includes information on NXX Code Activations is also available on the ATIS web site under the Document Center as "Intercompany Responsibilities Within The Telecommunications Industry."


    CenturyLink contact information is located in Wholesale Customer Contacts.

    For additional information, contact your CenturyLink Service Manager.

    Frequently Asked Questions (FAQs)

    1. How do I obtain an NXX Code?
    You can obtain an NXX Code by requesting one from the NANPA. Information on numbering assignments can be found on the NANPA web site.

    2. How are my NXX Codes activated within CenturyLink?
    Your NXX Codes are activated in the CenturyLink network as a normal course of business in accordance with the information you provide in the LERG. If, in some instances, additional routing information is required, CenturyLink recommends that you complete the "CenturyLink NPA NXX Code Request Routing Form."

    3. What happens if my trunk groups are not in place, or if I need to change the activation date of a new NXX Code?
    You are responsible for administering the NXX codes assigned to you. If the effective date for an NXX code activation changes, you will need to notify NANPA and make the necessary changes in the LERG.

    Last Update: March 13, 2014

    LERG™, CLLI™ and TPM™ are trademarks of Telcordia Technologies, Inc.
    NeuStar™ is a trademark of NeuStar, Inc.
    DID® is a registered trademark of CenturyLink™
    Common Language® is a registered trademark of Telcordia Technologies, Inc.