Local Routing Number - Overview

Overview

In the US, the LRN is a 10-digit number following the North American Numbering Plan (NANP). The LRN is stored in a database called a Service Control Point (SCP) that identifies a switching port for a local telephone exchange. Using LRN, when a phone number is dialed, the local telephone exchange queries or "dips" a routing database, usually the SCP, for the LRN associated with the subscriber. The LRN removes the need for the public telephone number to identify the local exchange carrier. If a subscriber changes to another telephone service provider, the current telephone number can be retained, and only the LRN needs to be changed. In addition to supporting service provider phone number portability, an LRN also supports the possibility of two other types of number portability: service portability (for example, ordinary service to ISDN) and geographic portability.