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Handbook for Illinois, Indiana, Michigan, Ohio, Wisconsin


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LNP Substitution 



As a carrier involved in porting telephone numbers, you most likely have already updated the Number Portability Administration Center (NPAC) database with your particular LRN and Global Title Translations (GTT) information.

If you are using AT&T for CNAM, LIDB, or CLASS, you probably entered the AT&T standard Alis STP point codes for these various services e.g. 243-250-005 for CNAM and 243-250-253 for LIDB when you updated the NPAC. However, when a CNAM or LIDB query is launched from your switch and the originating telephone number is ported, our database must first perform a query to the LNP platform in order to determine if the name still remains in our database.

If the LNP database returns our standard Alis STP point code, 243-250-005 in the case of CNAM, and 243-250-253 in the case of LIDB, we will direct the query to the same STP that launched the LNP query. From there the same LNP query is launched again, thus placing your query in an infinite loop.

This loop not only eliminates the return of your name information, it can severely impact the performance of out STP's. Consequently, we developed a means of rerouting these messages once we received the LNP information indicating the ported name resides in the AT&T database. Using a substitution table, we bypass the second LNP query and send the CNAM or LIDB request right into our database. From there, the correct database is polled, the appropriate information is returned.


The substitution form and instructions for  Number Manager GTT Substitution Data can be found in the Forms and Exhibits section.  To determine if this form is necessary in your situation, AT&T will need all three of the following criteria met: 

  1. You are using AT&T for CNAM, LIDB, or CLASS.

  2. You have A-Links with AT&T (direct SS7 connections from your end office to the AT&T Switching Transfer Point, STP).  

  3. You are performing LNP or Number Pooling from your end office and have a Local Routing Number (LRN) assigned in the NPAC.