LERG™ Routing Guide

The LERG Routing Guide is the most comprehensive routing data output available from TRA. Data supports the current local exchange network within the North American Numbering Plan (NANP) and identifies reported planned changes in the network. The LERG Routing Guide is primarily designed to be used for routing of calls by service providers (wireless, wireline, inter and intra exchange, etc.). It also supports functions such as networking planning and engineering, numbering administration and is used by companies, including many outside of the telecommunications industry, to support a wide range of business operations and planning needs. The LERG has been in existence since 1984 and provides a common basis for service providers within the NANP to directly report their numbering and routing information. The LERG is supported by integrated and quality-oriented industry processes and is similarly supported by TRA. Data in the LERG includes:


  • Operating Company Numbers, Company Names, Routing Contacts
  • Country Code Assignments
  • NPA Information (i.e., Area Codes)
  • LATA Codes By Region
  • Destination Codes (i.e. NPA NXX and Thousands-Blocks) (details on over 900,000 assignments)
  • Oddball NXXs (e.g. 911, 976)
  • Switching Entity Record detail (e.g. Equipment Type, V&H Coordinates)
  • Rate Center details (e.g. V&H Coordinates) and Localities (including county and postal codes)
  • Switch Homing Arrangements (tandem and other switch-to-switch interconnections)
  • Operator Access Tandem Codes (ATCs)
  • Location Routing Numbers (LRNs)


The LERG Routing Guide provided via the TRA Product Distribution System (PDS) includes a Microsoft Access database version of the data in addition to fix formatted data files. The Access database version of the LERG provides a graphical user interface front end to access and view data records using a TRA designed "form view" as well as Access "table views". The database requires users to have a local licensed copy of Access. Users with a basic knowledge of Microsoft Access can easily search for specific data elements, create customized queries, cross-relate data files, export data to other software (e.g. Microsoft Excel), generate files that can  serve as input files downstream operations support systems, etc.


Note: Equipment type - Switching System Codes (coded values regarding switch equipment types in the LERG) are assigned by Common Language. A spreadsheet of valid codes is available at www.commonlanguage.com. Click on “Common Language Store” in the lower left corner of the web page then, at the store site, choose SSC Codes Spreadsheet.


The following is an image of the user interface provided with each copy of the LERG. This image represents a very small sample example of all the data that is in the LERG. Data files are also included in the LERG, use of the user interface is optional. The TRA Catalog co-nations additional representations of LERG data.




Produced: first workday monthly

Distribution Frequency: monthly or quarterly (March, June, September, December)

Distribution Format(s): web download

LERG One Day Changes: Monthly subscribers may opt to be provided access to a password-protected web-based LERG One Day Changes Process at no additional charge. This process provides fixed-formatted data files reflecting daily changes to the primary data files.

Click here to request more information on the LERG. Data file specifications and the LERG General Section (includes glossary) are available for download.

Sample LERG Available

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LERG OnLine:

This easy-to-use web-based GUI application for monthly LERG subscribers is licensed on an enterprise-basis. LERG OnLine data is updated daily instead of monthly. The LERG OnLine data can be downloaded to your local environment, which then, as with the LERG Routing Guide data, can be integrated into other applications.

The following is an example of the interface.