One challenging piece of a OCS / Lync Server Enterprise Voice deployments, in certain areas of the United States, is determining what NPA/NXX (NPA-NXX-xxxx) combinations are local vs long distance. For example, Dallas can have both local and long distance numbers within the 972 area code. Knowing what combinations are local vs. long distance is essential for creating accurate routing tables.
There are several methods to obtain the local vs long distance NPA/NXX combinations.
- Trial and error (Everyone's Favorite!)
- Customer Provided (When it is wrong who will they blame?)
- Telco Provided (When has a telco been useful?)
- Voice Partner Provided (Decent chance of getting close, but you may not have one to ask)
- Local Calling Guide website (Decent chance of getting close and it is a click away)
All of the above sources can have incorrect or incomplete information. However, I've found Local Calling Guide website to be a great starting point to create the routing tables and then use the other sources to fill in any holes, if necessary.
To determine what NPA/NXX combinations are local to your customer go the Local Calling Guide website and click "Search Area Code/Prefix/OCN".
In the "NPA" box enter the customers area code. In the "NXX" box enter the next three digits of the customers phone number (NPA-NXX-xxxx). Then click "Submit"
Information will come up regarding the NPA-NXX you entered. Click the Rate Centre (Dallas in the example above).
To see the complete list click on See All Local Prefixes.
Not only will the list be complete (or at least what is in the database), the list will also be displayed in a delimited format that can easily be manipulated in a spreadsheet or database.